CN118251264A - Hot gas filtration with enhanced compartment flow distribution via dual filter configuration - Google Patents

Abstract

A filtration system includes a filter housing, a plurality of elongated bag filters disposed in the filter housing, and a plurality of cylindrical pleated filters disposed in the filter housing. A plurality of elongated bag filters and a plurality of cylindrical pleated filters are arranged to filter gas passing through the filter housing. Further, the plurality of elongated bag filters has an average length that is at least twice the average length of the plurality of cylindrical pleated filters.

Description

Hot gas filtration with enhanced compartment flow distribution via dual filter configuration

Technical Field

The present invention relates generally to filtration systems and in particular to filtration systems for gases.

Background

Many parts of the world are implementing increasing environmental regulations and controls that focus on reducing airborne pollutants and emissions from certain industrial sources such as power plants and material production facilities. It is possible to control pollutants and emissions from various industrial sources by separating undesirable particulate matter carried in the gas stream by means of, for example, fabric filtration. Such fabric filtration is accomplished in a dust removal apparatus known in the industry as a "baghouse".

Conventional baghouses typically include a housing divided into two chambers by a tube sheet. One chamber is a "dirty air" chamber that communicates with the inlet and receives "dirty" or particulate laden gas from a source at the factory. The other chamber is a "clean air" chamber that receives the filtered clean gas and communicates with an outlet to direct the clean gas out of the baghouse. In a conventional baghouse, a plurality of relatively long cylindrical fabric filters (commonly referred to as "bag filters") are suspended from a tube sheet in a dirty air plenum. Each bag filter has a closed lower end and is mounted attached to a cage structure. Each bag is mounted to the tube sheet at its upper end and depends vertically downwardly into the dirty air plenum. The upper end portions of the bag filters are open and the interior of each bag filter is in fluid communication with a clean air plenum.

In operation, particulate laden gas is directed into the dirty air chamber. As the particulate laden gas flows through the baghouse, the particulates carried by the gas come into contact with the exterior of the baghouse media and accumulate on or in the media. Alternatively, particulates may also separate from the airflow and fall into the accumulator chamber at the lower portion of the dirty air plenum before reaching the bag filter. The filtered gas then passes through the media of the fabric filter bag, into the interior of the filter bag, flows to the clean air plenum, and out through the outlet. Although many baghouses are fabricated in this basic configuration, there may be many operational and structural differences between the baghouses.

In view of the various drawbacks associated with conventional baghouse filter systems, it would be desirable in the industry to have a filter assembly system that provides many of the advantages of relatively long bag filters while also addressing some of the above-described drawbacks.

Embodiments of the present invention provide such a filter assembly system. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

Disclosure of Invention

Embodiments of the present invention relate to the use of both pleated and long bag filters, which are shown to achieve enhanced compartment flow distribution results at advantageously lower operating pressure differential conditions. One feature of the present invention involves the simultaneous use of multiple pleated filters in combination with multiple conventional long bag filters, both types of filters designed to operate continuously at 500 degrees Fahrenheit. In this context, continuous operation at 500 degrees Fahrenheit includes continuous filtration of one or more gases having an average temperature of 500 degrees Fahrenheit. Conventional industrial filtration applications do not include the simultaneous use of both pleated and long bag filters, both operating continuously at 500 degrees fahrenheit.

In one aspect, embodiments of the present invention provide a filtration system including a filter housing, a plurality of elongated bag filters disposed in the filter housing, and a plurality of cylindrical pleated filters disposed in the filter housing. A plurality of elongated bag filters and a plurality of cylindrical pleated filters are arranged to filter gas passing through the filter housing. Further, the average length of the plurality of elongated bag filters is at least twice the average length of the plurality of cylindrical pleated filters.

In a particular embodiment, the first filter media of the plurality of elongated bag filters and the second filter media of the plurality of cylindrical pleated filters are each configured to continuously filter gas having an average temperature of 500 degrees Fahrenheit.

In certain embodiments, the average length of the plurality of elongated bag filters is between two and five times the average length of the plurality of cylindrical pleated filters. Embodiments of the present invention also include those wherein the filter housing is rectangular and the plurality of elongated bag filters and the plurality of cylindrical pleated filters are arranged in alternating rows. In such an arrangement, the number of elongated bag filters may be equal to or nearly equal to the number of cylindrical pleated filters.

In an alternative embodiment, the filter housing is rectangular and the plurality of elongated bag filters and the plurality of cylindrical pleated filters are arranged in rows, wherein every two rows of elongated bag filters are separated by a row of cylindrical pleated filters. In such an arrangement, there are at least three elongated bag filters for every two cylindrical pleated filters.

In yet another embodiment, the filter housing is rectangular and the plurality of elongated bag filters and the plurality of cylindrical pleated filters are arranged in rows, wherein every third row of elongated bag filters is separated by a row of cylindrical pleated filters. In such an arrangement, there are at least five elongated bag filters for every two cylindrical pleated filters.

In some embodiments, the hopper is located below and supports the filter housing. Each of the plurality of elongated bag filters may range in length from 4 meters to 15 meters, and the plurality of cylindrical pleated filters may range in length from 1 meter to 4 meters. In a particular embodiment, each of the plurality of cylindrical pleated filters includes a media sheet having radially projecting pleats extending longitudinally along the filter element. In a more particular embodiment, each of the plurality of cylindrical pleated filters includes an annular upstream end cap and a cylindrical downstream end cap, the upstream end cap defining a central opening and the downstream end cap closing a downstream end of the filter.

In further embodiments, each of the plurality of elongated bag filters includes a media bag supported by a frame, wherein each elongated bag filter has an open upstream end and a closed downstream end. Embodiments of the invention include a filter housing having an inlet for receiving hot gas and having an outlet in a lower portion of the filter housing for discharging filtered hot gas and in an upper portion of the filter housing.

In certain embodiments, the pressure differential between the inlet and outlet is less than 85% of the pressure differential that would be produced if each of the plurality of cylindrical pleated filters were replaced with a similar number of elongated bag filters. In further embodiments, the pressure differential between the inlet and outlet is less than 80% of the pressure differential that would be created if each of the plurality of cylindrical pleated filters were replaced with a similar number of elongated bag filters. In yet another embodiment, the pressure differential between the inlet and outlet is less than or equal to 76% of the pressure differential that would be created if each of the plurality of cylindrical pleated filters were replaced with a similar number of elongated bag filters.

In another particular embodiment, the gas passing through the filter housing is filtered in parallel. For purposes of the present application, "parallel filtration" refers to a filter arrangement in which gas flows through either one of the cylindrical pleated filters or one of the elongated bag filters, but not both. This parallel filter arrangement is distinct from an in-line filter arrangement in which the flow of gas through the filter housing is filtered through at least one of the cylindrical pleated filters and then through at least one of the elongated bag filters.

Other aspects, objects, and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and form a part of this specification, illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a perspective view of a gas filtration system constructed in accordance with an embodiment of the invention;

FIG. 2 is a perspective view of a cylindrical pleated filter according to an embodiment of the invention;

FIG. 3 is a perspective view of an elongated bag filter disassembled according to an embodiment of the invention; and

FIG. 4 is a side view of a plurality of pleated filter elements for use in a pulse jet baghouse in accordance with an embodiment of the invention;

FIG. 5 is a bottom perspective view of a plurality of pleated filter elements in the baghouse of FIG. 4;

FIG. 6 is a schematic illustration of a pulse jet baghouse with a plurality of pleated filter elements mounted thereto;

FIG. 7 is a graphical illustration showing the relationship between differential pressure and the number of pleated filters;

FIG. 8 is a horizontal cross-sectional view of the pleated filter element of FIG. 2;

FIG. 9 is a side view of a support core used in the pleated filter element of FIG. 2;

FIG. 10A is a perspective cross-sectional view of an example of an open end cap and support core that may be used with the pleated filter element of FIG. 2;

FIG. 10B is a schematic cross-section of an open end cap similar to FIG. 10A, but schematically indicating how the open end cap engages with felt wire protrusions on the modified tubesheet to seal against unfiltered air flow; and

Fig. 11 is a perspective view of a closed end cap, pleated filter element and support core that may be used with the pleated filter element of fig. 2.

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

In view of the problems and challenges described above with respect to conventional baghouse filter systems, there is an interest in replacing known fabric filter bags with pleated media cartridges to increase the effective filtration area while occupying the same or less space within the baghouse. However, there are certain obstacles to easy replacement of fabric filter bags with pleated media cartridges. In some baghouse designs, the fabric filter bags may have a length of about four meters or more. The clean air plenum typically has a headroom of substantially less than four meters (e.g., about two meters). Because the fabric filter bags are collapsible, flexible, and non-rigid, locating the fabric filter bags in the baghouse is generally not an issue. Because of the limited access space in the clean air plenum, if a relatively long and rigid pleated media cartridge is fully capable of being installed, it cannot be installed without significant manipulation.

In order to occupy the same space within the baghouse as the fabric filter bags, the pleated media cartridges are relatively long in length and can be up to about four meters or more in length. In the embodiments of the invention described below, the pleated media cartridge may be as short as one meter in length, or in some cases even shorter, and as long as four meters in length, although longer lengths are also contemplated.

Fig. 1 is a perspective view of a filtration system 100, and more specifically a gas filtration system 100, constructed in accordance with an embodiment of the invention. The filtration system 100 includes an assembly of filter elements 102 disposed within a filter housing 104 supported by a hopper 105. The filter assembly 102 includes a plurality of elongated bag filters 106 disposed in a filter housing 104 and a plurality of cylindrical pleated filters 108 also disposed in the filter housing 104.

Fig. 2 is a perspective view of a cylindrical pleated filter 108 according to an embodiment of the invention. Fig. 3 is a perspective view of an elongated bag filter 106 disassembled according to an embodiment of the invention. A plurality of elongated bag filters 106 and a plurality of cylindrical pleated filters 108 are arranged to filter gas passing through the filter housing 104. Moreover, in certain embodiments, the average length of the plurality of elongated bag filters 106 is at least twice the average length of the plurality of cylindrical pleated filters 108.

In the filtration system 100 of fig. 1, there is an assembly 102 of filter elements for a filter housing 104 for gas filtration. In certain embodiments, the filter assembly 102 includes a uniformly arranged and uniformly distributed grouping of elongated bag filters 106 and cylindrical pleated filters 108 configured to filter gas passing through the filter housing 104. As described above, the length of the elongated bag filter 106 is typically at least twice the length of the cylindrical pleated filter 108.

In certain applications, such as filtering hot gaseous emissions emitted as a byproduct of a cement manufacturing process, the elongated filter media 112 of the plurality of elongated bag filters 106 and the pleated filter media 116 of the plurality of cylindrical pleated filters 108 are each configured to continuously filter gases having an average temperature of 500 degrees Fahrenheit.

Referring to fig. 4-6, an exemplary filter chamber application and method of using the filter cartridge 108 including pleated filter media 116 is illustrated. The filter cartridge 108 is installed into a tube sheet 168 of a filter chamber 170 (e.g., a reverse pulse filter chamber). The filter cartridge 108 may be sealed to the tubesheet 168. For high temperature applications, such as cement kiln applications, the pleated filter element 116 may be operated continuously at an elevated temperature of at least 500 degrees Fahrenheit for at least several hours to remove particulates from the air stream passing through the pleated filter element 116 from the unfiltered air inlet 172 to the filtered air outlet 174.

The filter cartridge 108, along with its pleated filter element 116, is periodically back-pulsed in this application to dislodge the filter cake collected on the pleated filter element 116. For example, as schematically shown in fig. 6, the filter chamber 170 includes a compressed air source 180 connected to a back pulse compressed air manifold 182 via a solenoid valve 184. In some embodiments, a hopper 176 is positioned below the filter chamber 170 and supports the filter chamber. Hopper 176 collects filter cake that drops off after reverse pulsing of pleated filter element 116.

The controller 186, at timed intervals or upon sensing a pressure differential indicative of the cake load, will periodically open the solenoid valve 184 to generate air injection pulses through the manifold 182 that reverse pulse air through the filter cartridge 108 to dislodge the cake accumulated on the pleated filter element 116.

When installed in a filter chamber 170 (e.g., a conventional pulse jet baghouse), the filter cartridge 108 is in a parallel circuit with other similar filter cartridges 108 along a tube sheet 168 that divides the filter chamber into a clean chamber and a dirty chamber. Unfiltered or dirty gas passes from the inlet 172 through the pleated filter element 116 of the filter cartridge 108 to remove particulates. This in turn produces filtered air that is transferred into the cleaning chamber, which can exit the chamber 170 through the outlet 174. Periodically, the pulse jet system will pulse air to remove the "filter cake" from the pleated filter element 116 for collection at the bottom of the filter chamber 170 and thus regenerate the life of the pleated filter media 116 of the filter cartridge 108. As noted above, the cylindrical pleated filter 108 is particularly useful in high temperature applications, such as cement kiln filtration applications, where the operating temperature is typically greater than 500 degrees fahrenheit. This may occur for long term continuous operation of several hours, days or weeks.

Referring again to fig. 1, in a particular embodiment, the filter housing 104 is rectangular and a plurality of elongated bag filters 106 and a plurality of cylindrical pleated filters 108 are arranged in rows, wherein every third row of elongated bag filters 106 is separated by a row of cylindrical pleated filters 108. In such an arrangement, there are at least five elongated bag filters 106 for every two cylindrical pleated filters 108.

In an alternative embodiment, the filter housing 104 is rectangular and the plurality of elongated bag filters 106 and the plurality of cylindrical pleated filters 108 are arranged in rows, wherein every two rows of elongated bag filters 106 are separated by a row of cylindrical pleated filters 108. In such an arrangement, there are at least three elongated bag filters 106 for every two cylindrical pleated filters 108.

The filter housing 104 has an inlet 110 for receiving hot gas. The inlet 110 may be located in a lower portion of the filter housing 104 or in the hopper 105, as shown in fig. 1. The filter housing 104 has an outlet 114 for discharging the filtered hot gas, the outlet 114 being located in an upper portion of the filter housing 104.

Because both the elongated bag filter 106 and the cylindrical pleated filter 108 are used, the filtration system 100 exhibits improved compartment flow distribution as compared to conventional filtration systems utilizing only the elongated bag filter 106. The improved compartment flow distribution results in a lower differential pressure drop. A decrease in the pressure differential between the inlet 110 and the outlet 114 is indicative of an increase in the performance of the filtration system 100.

One of ordinary skill in the art will recognize that embodiments of the gas filtration system 100 disclosed herein provide for gas to pass through the filter housing 104 while being filtered in parallel. As explained above, in the context of the present application, "parallel filtration" refers to a filter arrangement in which gas flows through either one of the cylindrical pleated filters 108 or one of the elongated bag filters 106, but not both. This parallel filter arrangement is distinct from an in-line filter arrangement in which the flow of gas through the filter housing 104 is filtered through at least one of the cylindrical pleated filters 108 and then through at least one of the elongated bag filters 106.

FIG. 7 is a graphical illustration showing the relationship between differential pressure and the number of pleated filters. As shown, empirical test data for a filtration system with an elongated bag filter 106 shows a pressure differential of about 7.1. Fig. 7 includes test data for differential pressure in three exemplary filtration systems 100 having a combination of an elongated bag filter 106 and a cylindrical pleated filter 108. The first system having 152 elongated bag filters 106 and 152 cylindrical pleated filters 108 had a pressure differential of about 5.9. The second system having 185 elongated bag filters 106 and 119 cylindrical pleated filters 108 had a pressure differential of about 5.7. A third system having 219 elongated bag filters 106 and 85 cylindrical pleated filters 108 had a pressure differential of about 5.4.

According to the above test numbers, the pressure differential between the inlet 110 and the outlet 114 of the first system described above is less than 85% of the pressure differential that would be created if each of the plurality of cylindrical pleated filters 108 were replaced with a similar number of elongated bag filters 106. The pressure differential between the inlet 110 and the outlet 114 of the second system described above is less than 80% of the pressure differential that would be created if each of the plurality of cylindrical pleated filters 108 were replaced with a similar number of elongated bag filters 106. The pressure differential between the inlet 110 and the outlet 114 of the third system described above is less than or equal to 76% of the pressure differential that would be created if each of the plurality of cylindrical pleated filters 108 were replaced with a similar number of elongated bag filters 106.

Fig. 8 is a horizontal cross-sectional view of a cylindrical pleated filter 108 according to an embodiment of the invention. Fig. 9 is a side view of the support core 222 in the cylindrical pleated filter 108. Fig. 10A is a perspective cross-sectional view of an exemplary open end cap 224 and support core 222 for use in a cylindrical pleated filter 108. Fig. 10B is a schematic cross-section of an open end cap 224 similar to fig. 10A, but schematically indicating how the open end cap 222 functions to block unfiltered airflow. Fig. 11 is a perspective view of a closed end cap 230, a portion of pleated filter media 116, and a support core 222 incorporated into a cylindrical pleated filter 108.

The pleated filter element 116 is formed of a filter media composite 190 (also referred to as a composite or laminate composite), as shown in fig. 8, to include a fibrous support layer 180 and a filter layer 200 bonded to the fibrous support layer. When disposed in the filter cartridge 108 of fig. 2, the fiber support layer 180 is positioned along the central cavity 160 and faces radially inward, as depicted in fig. 8. The filter layer 200 is positioned on the radially outer surface of the fiber support layer 180 for a first beginning of an incoming unfiltered air flow.

To provide additional support to the filter media composite 190 when incorporated into the cylindrical pleated filter 108, a support core 222 may be used, as shown in fig. 8. The support core 222 is arranged to contact and support the fiber support layer 180. The support core 222 may be a metal perforated cylindrical tube, as illustrated in fig. 9. The support core 222 supports the inner periphery of the cylindrical pleated filter 108 along the central cavity 160. In particular, the support core 222 is disposed in contact with the inwardly facing pleat tips 220.

As first shown in fig. 2, and in greater detail in fig. 10A, an open end cap 224 is attached to a first end 226 of the cylindrical pleated filter 108. For example, the open end cap 224 may include an annular metal disc with a central opening and with an annular potting well of potting adhesive material that bonds and seals the top end of the pleated filter media 116 to the open end cap 222 to prevent unfiltered bypass therebetween.

As first shown in fig. 2, and in greater detail in fig. 10A, an open end cap 224 is attached to a first end 226 of the cylindrical pleated filter 108. For example, the open end cap 224 may include an annular metal disc with a central opening and with an annular potting well of potting adhesive material that bonds and seals the top end of the pleated filter media 116 to the open end cap 222 to prevent unfiltered bypass therebetween.

The opening 224 may include a sealing structure 228 disposed about the first end 226 of the cylindrical pleated filter 108, which may take the form of an annular rib that may engage an annular projection (shown in FIG. 10B) along the tube sheet 168. As shown, the tubesheet 168 has protrusions that may include stitched and felted (stitched-and-felted) round metal clips 229 with a filter metal top that fits over the metal clips. The stitched and felted round metal clip 229 may be inserted first into the tube sheet hole 178, then vertically inserted into the filter, and the metal top of the cylindrical pleated filter 108 pushed down onto the metal clip to seal the cylindrical pleated filter 108, thereby preventing bypass (see, e.g., fig. 5, showing the cylindrical pleated filter installed in the tube sheet 168). However, it will be appreciated that any seal that can be used in a filter cartridge may be employed, including annular radial and axial seal gaskets that can seal against the tubesheet 168 when in use, depending on the configuration of the tubesheet 168 or filter chamber 170.

The open end cap 224 may include a sealing structure 228 disposed about the first end 226 of the cylindrical pleated filter 108, which may take the form of an annular rib that may engage an annular projection (shown in fig. 10B) along the tube sheet 168. As shown, the tubesheet 168 has protrusions that may include a sewn and felted round metal clip 229 with a filter metal top that fits into the metal clip. The stitched and felted round metal clip 229 may be inserted first into the tube sheet hole 178, then vertically inserted into the filter, and the metal top of the cylindrical pleated filter 108 pushed down onto the metal clip to seal the cylindrical pleated filter 108, thereby preventing bypass (see, e.g., fig. 5, showing the cylindrical pleated filter installed in the tube sheet 168). However, it will be appreciated that any seal that can be used in a filter cartridge may be employed, including annular radial and axial seal gaskets that can seal against the tubesheet 168 when in use, depending on the configuration of the tubesheet 168 or filter chamber 170.

As first shown in fig. 2, and in greater detail in fig. 11, a closed end cap 230 is attached to a second end 232 of the cylindrical pleated filter 108. The closed end cap 230 may include a metal chassis that holds a material 231, such as a potting adhesive material, as a sealant to the second end 232 of the cylindrical pleated filter 108 to prevent unfiltered bypass at the second end 232.

Further, at least one support strap 234 (shown in fig. 2) may be positioned in surrounding supporting relation to the cylindrical pleated filter 108 in a spaced apart position between the closed end cap 230 and the open end cap 224. The support band 234 provides restraint to support and prevent the plurality of pleats 236 from bursting when the back pulse is applied.

The support band 234 is disposed to contact the radially outward facing pleat tips and may contact the filter layer. For example, a metal belt suitable for high temperature applications may be used as the support belt 234.

Both the fibrous support layer 180 and the filter layer 200 are in the form of pleats to provide a plurality of pleats 236, as shown in FIG. 8. Preferably, the fiber support layer 180 is bonded to the filter layer 200 by a means other than a cured hardener. In this way, the filter layer 200 may not be blocked by the cured hardener and may maintain the filtration efficiency and permeability of the filter media composite 190.

The cylindrical pleated filters 108 each have a cylindrical arrangement of pleated filter media 116 having radially projecting pleats 225 extending longitudinally along the pleated filter media 116, having an annular upstream end cap 224 defining a central opening 160 and a cylindrical downstream end cap 230 closing a downstream end 232 of the cylindrical pleated filter 108.

In embodiments of the invention more specific than the above-described embodiments, the average length of the plurality of elongated bag filters 106 is between two and five times the average length of the plurality of cylindrical pleated filters 108. Embodiments of the present invention also include those wherein the filter housing 104 is rectangular and the plurality of elongated bag filters 106 and the plurality of cylindrical pleated filters 108 are arranged in alternating rows. In such an arrangement, the number of elongated bag filters 106 may be equal to or nearly equal to the number of cylindrical pleated filters 108.

In typical applications, the length of each of the plurality of elongated bag filters 106 may range from 4 meters to 15 meters, while the length of the plurality of cylindrical pleated filters 108 may range from 1 meter to 4 meters. In certain embodiments, each of the plurality of cylindrical pleated filters 108 includes a pleated filter media 116 having radially protruding pleats 225 (see fig. 8) extending longitudinally along the pleated filter media 116. In a more particular embodiment, each of the plurality of cylindrical pleated filters 108 includes an annular upstream end cap 224 (see fig. 10A) defining a central opening 160 and a cylindrical downstream end cap 230 (see fig. 10A) closing a downstream end 232 of the cylindrical pleated filter 108.

In further embodiments, each of the plurality of elongated bag filters 106 includes the aforementioned elongated filter media 112 supported by the frame 113, wherein each elongated bag filter 106 has an open upstream end 226 and a closed downstream end 232, as shown in fig. 2. Further, as described above, each of the elongated bag filter 106 and the cylindrical pleated filter 108 includes a high temperature medium capable of continuous operation at 500 degrees Fahrenheit.

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.

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) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Unless otherwise indicated, the terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to"). 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.

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. Furthermore, 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.

Claims (20)

1. A filtration system, comprising:

A filter housing;

a plurality of elongated bag filters disposed in the filter housing;

A plurality of cylindrical pleated filters disposed in the filter housing;

Wherein the plurality of elongated bag filters and the plurality of cylindrical pleated filters are arranged to filter gas passing through the filter housing, and wherein an average length of the plurality of elongated bag filters is at least twice an average length of the plurality of cylindrical pleated filters.

2. The filtration system of claim 1, wherein a first filter media of the plurality of elongated bag filters and a second filter media of the plurality of cylindrical pleated filters are each configured to continuously filter the gas having an average temperature of 500 degrees fahrenheit.

3. The filtration system of claim 1, wherein an average length of the plurality of elongated bag filters is between two and five times an average length of the plurality of cylindrical pleated filters.

4. The filtration system of claim 1, wherein the filter housing is rectangular, and wherein the plurality of elongated bag filters and the plurality of cylindrical pleated filters are arranged in alternating rows.

5. The filtration system of claim 4, wherein the number of elongated bag filters is equal to the number of cylindrical pleated filters.

6. The filtration system of claim 1, wherein the filter housing is rectangular, and wherein the plurality of elongated bag filters and the plurality of cylindrical pleated filters are arranged in rows, wherein each two rows of elongated bag filters are separated by a row of cylindrical pleated filters.

7. The filtration system of claim 6, wherein there are at least three elongated bag filters for each two cylindrical pleated filters.

8. The filtration system of claim 1, wherein the filter housing is rectangular, and wherein the plurality of elongated bag filters and the plurality of cylindrical pleated filters are arranged in rows, wherein every third row of elongated bag filters is separated by a row of cylindrical pleated filters.

9. The filtration system of claim 8, wherein there are at least five elongated bag filters for each two cylindrical pleated filters.

10. The filtration system of claim 1, further comprising a hopper positioned below and supporting the filter housing.

11. The filtration system of claim 1, wherein each of the plurality of elongated bag filters ranges in length from 4 meters to 15 meters.

12. The filtration system of claim 1, wherein each of the plurality of cylindrical pleated filters ranges in length from 1 meter to 4 meters.

13. The filtration system of claim 1, wherein each of the plurality of cylindrical pleated filters comprises a media sheet having radially protruding pleats extending longitudinally along the filter element.

14. The filtration system of claim 13, wherein each of the plurality of cylindrical pleated filters comprises an annular upstream end cap and a cylindrical downstream end cap, the upstream end cap defining a central opening and the downstream end cap closing a downstream end of the filter.

15. The filtration system of claim 1, wherein each of the plurality of elongated bag filters comprises a media bag supported by a frame, wherein each elongated bag filter has an open upstream end and a closed downstream end.

16. The filtration system of claim 1, wherein the filter housing has an inlet for receiving hot gas and an outlet in a lower portion of the filter housing for discharging filtered hot gas.

17. The filtration system of claim 16, wherein the pressure differential between the inlet and outlet is less than 85% of the pressure differential that would be created if each of the plurality of cylindrical pleated filters were replaced with a similar number of elongated bag filters.

18. The filtration system of claim 16, wherein the pressure differential between the inlet and outlet is less than 80% of the pressure differential that would be created if each of the plurality of cylindrical pleated filters were replaced with a similar number of elongated bag filters.

19. The filtration system of claim 16, wherein the pressure differential between the inlet and outlet is less than or equal to 76% of the pressure differential that would be created if each of the plurality of cylindrical pleated filters were replaced with a similar number of elongated bag filters.

20. The filtration system of claim 1, wherein gas passing through the filter housing is filtered in parallel.