Patent Publication Number: US-2021170311-A1

Title: Filter element, filter, filter device, and method of use

Description:
BACKGROUND OF THE INVENTION 
     A variety of filters are available to filter fluids (gasses and liquid). However, some filters, including some filters that are exposed to reverse flow, exhibit limited filtration life due to insufficient mechanical strength and/or are costly to produce. 
     The present invention provides for ameliorating at least some of the disadvantages of the prior art. These and other advantages of the present invention will be apparent from the description as set forth below. 
     BRIEF SUMMARY OF THE INVENTION 
     An embodiment of the invention provides a porous filter element comprising a hollow cylindrical porous metal medium having a first end and a second end, the hollow cylindrical porous metal medium comprising a plurality of pleats longitudinally arranged along an axis from the first end to the second end, each pleat comprising a plurality of portions each having a height to width aspect ratio of about 1:≥1. 
     In another embodiment, a porous filter is provided, comprising an embodiment of the porous filter element. Typically, an embodiment of a porous filter comprises two or more embodiments of porous filter elements connected together. 
     Embodiments of the invention also comprise systems including the filters, and methods of filtration including passing fluid through embodiments of the porous filter element. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is a perspective view of a filter element according to an embodiment of the invention, also showing a plurality of pleats longitudinally arranged along an axis from the first end of the filter element to the second end. 
         FIG. 2A  is a perspective partial cut away view of the filter element shown in  FIG. 1 , also showing a tapered end;  FIG. 2B  is a cross-sectional view of filter element shown in  FIG. 1 ;  FIG. 2C  is an enlarged view of the circled detail shown in  FIG. 2B ; and  FIG. 2D  is an enlarged view of detail F shown in  FIG. 2B , showing spacing and center to center distances between portions of a pleat in the z-direction (the longitudinal direction) according to an embodiment of the invention. 
         FIGS. 3A-3C  illustrate different configurations of portions of the pleats according to embodiments of the invention, wherein, when viewing the top of the pleat, the different configurations have different height (H) to width (W) aspect ratios. In  FIG. 3A , the portion has a pointed oval appearance, with a height to width aspect ratio of 1:&gt;1 (shown in this Figure as 2:&gt;1); in  FIG. 3B , the portion has a generally circular appearance, with a height to width aspect ratio of 1:1; and in  FIG. 3C  the portion has a rounded oval appearance, with a height to width aspect ratio of 1:&gt;1 (shown in this Figure as 2.7:&gt;1). 
         FIG. 4  shows a side view of a configuration of a portion of pleat illustrated in  FIG. 1  showing the depth and height of the portion. 
         FIG. 5  shows, in an end view of a filter element with a closed end, spacing of the pleats in the circumferential direction, wherein the spacing between portions on adjacent pleats can be spaced at an angle x in the range of about 0.9° to about 180° with respect to the center of the filter element. 
         FIGS. 6A and 6B  are perspective views of a filter according to an embodiment of the invention comprising two embodiments of filter elements connected together.  FIG. 7A  shows the top (open) end, and  FIG. 7B  shows the bottom (closed end). 
         FIG. 7A  is a perspective view of a filter according to another embodiment of the invention, comprising an embodiment of a filter element with a threaded end fitting at one end of the element, wherein the other end is closed.  FIG. 7B  shows a perspective view of the threaded end fitting. 
         FIG. 8A  is a perspective view of a filter according to another embodiment of the invention, comprising two embodiments of filter elements connected together with a threaded end fitting at one end of one of the elements (wherein the other end of the element is open), wherein the other element has an open end (connected to the open end of the first element) and a closed end.  FIG. 8B  shows a cross-sectional view of the filter shown in  FIG. 8A , and  FIG. 8C  shows an enlarged view of detail B in  FIG. 8B , showing a threaded fitting that can be integral to the filter element or welded to the open end of the first filter element. 
         FIG. 9A  is a cross-sectional view of a filter according to another embodiment of the invention, comprising three embodiments of filter elements connected together with a venturi end fitting at one end of one of the elements (wherein the other end of the element is open), wherein the middle element is open and both ends (connected to the open ends of the first and third elements), and the third element has an open end (connected to the open end of the middle element) and a closed end.  FIG. 9B  shows an enlarged view of detail B in  FIG. 9B , showing the open ends welded together. 
         FIGS. 10A-10C  show various views of an illustrative filter system according to an embodiment of the invention, comprising a plurality of filters.  FIG. 10A  shows a cross-sectional side view;  FIG. 10B  shows a cross-sectional top view, and  FIG. 10C  shows a cross-sectional bottom view. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with an embodiment of the invention, a porous filter element is provided, comprising a hollow cylindrical porous metal medium having a first end and a second end, the hollow cylindrical porous metal medium comprising a plurality of pleats longitudinally arranged along an axis from the first end to the second end, each pleat comprising a plurality of portions each having a height to width aspect ratio of about 1:≥1. In a typical embodiment, the height to width aspect ratio is about 1:&gt;1, preferably, at least 1.5:&gt;1, in some embodiments, 2:&gt;1, or more. 
     In another embodiment, a porous filter comprises an embodiment of the porous filter element. A porous filter can include one filter element, or a plurality of filter elements, for example, at least two filter elements, at least 5 elements, at least 10 elements, or more. Alternatively, or additionally, an embodiment of a porous filter can comprise an embodiment of at least one porous filter element wherein the porous filter element includes a fitting at one, or both, ends. 
     Embodiments of filters can include one or more separate filters, e.g., arranged as a plurality of separate tubes in a filter system. 
     Embodiments of the invention also comprise filter systems including the filters, and methods of filtration including passing fluid through embodiments of the porous filter element. In a preferred embodiment of a method of filtration, the fluid to be filtered is passed from the outside of the filter element into the interior. More preferably, after a fluid is filtered by passing it through the filter element, a cleaning fluid is passed through the filter in the opposite direction of filtration, e.g., involving reverse pulsing. 
     In an embodiment, a filter system comprises a plurality of filters arranged vertically. In a preferred embodiment of the system, the system comprises two or more filter modules, each filter module comprising a plurality of filters. Alternatively, or additionally, an embodiment of the filter system includes a reverse pulsing system. 
     The configuration of the portions of the porous filter elements can be varied for different applications. For example, for some applications that involve filtering solid particulates in a gas stream, and subsequently reverse pulsing, minimizing the horizontal surface of the portions (e.g., making the height:width aspect ratio of greater than 1) can be desirable. 
     Either, or both, ends of the filter element can be open or closed, e.g., one end can be open and the other end closed. Either end, or both ends, can include an end cap, and end caps can be open or closed. A closed end can be integral with the filter element, or provided by a separate end cap. Either end, or both ends, of the filter element can include a fitting, and fittings can be different at each end. 
     In some embodiments, at least one end, sometimes both ends, of the filter element are tapered such that the depth of the portions at the end flare out to meet the outside diameter of the filter element (see, for example,  FIG. 2A ). This can provide for increased bend strength if desired for some applications. 
     Advantageously, filters and filter elements according to embodiments of the invention can have at least about 1.2 times (in preferred embodiments, at least about 1.5 times) more area in the same volume as a conventional cylinder. Moreover, filters and filter elements can allow for a reduced vessel (e.g., housing) diameter, which reduces cost and footprint. 
     In another advantage, filter elements can have a modular design, allowing for different lengths of filters with different fittings, e.g., national pipe taper (NPT), blind end (closed end cap), guide pin, o-ring, etc. Fittings can be attached to filter elements before or after sintering. In those embodiment of filters including two or more filter elements, elements can be connected in a variety of ways, e.g., via fittings and/or welding. 
     For industrial applications in particular, filters and filter elements have excellent mechanical strength, having been tested for over 20,000 blowback cycles and over 200,000 fatigue cycles in laboratory tests. 
     Each of the components of the invention will now be described in more detail below, wherein like components have like reference numbers. 
     In the illustrated embodiment shown in  FIGS. 1 and 2A , a filter  1000  comprises a porous filter element  500  comprising a hollow cylindrical porous metal medium  50  having a hollow interior  55  including an interior surface  55 A defining the hollow interior, a first end  51 , and a second end  52 . The filter element includes a plurality of pleats  100  longitudinally arranged along an axis A from the first end to the second end, each pleat comprising a plurality of portions  150  having a height to width aspect ratio of 1:≥1. Typically, when viewed from the side (e.g., as shown in  FIGS. 2B and 2C ), the top surfaces  150 A of the portions are slightly convex or slightly planar, rather than concave. 
     While there can be a gap between consecutive portions, in the illustrated embodiments, the consecutive portions are connected by a bridge  175 . The presence of a bridge can be desirable in allowing for increased surface area and increased mechanical strength of the element. Typically, when viewed from the side (e.g., as shown in  FIGS. 2B and 2C ), the top surface  175 A of the bridge is lower than the top surface  150 A of the portions. 
     As shown in  FIGS. 1, 2B and 2C  the interior surface  55 A includes concave openings  75 , communicating with hollow interiors  80  of each portion, the portions being closed at the top (covered by top surfaces  150 A). 
     In some embodiments, at least one end of the filter element is tapered such that the depth of the portions at the end flare out to meet the outside diameter of the filter element. In the embodiment shown in  FIG. 2A , the end  51  of the filter element has a taper  51 A, such that the depth of the portions  150 ′ at the end flares out to meet the outside diameter  51 ′ of the filter element. If desired, both ends of a filter element can be similarly or identically tapered. 
     As noted above, either end, or both ends, of the filter or filter element, can include an end cap, and end caps can be open or closed.  FIGS. 2B, 6B, 7A, 8A, 8B, and 9A  show an end cap  200 . In the embodiment illustrated in  FIGS. 6A, 6B, 7A, 8A, 8B, and 9A , porous filter element  500  is closed at one end with an end cap, porous filter element  500 A as illustrated in  FIGS. 6A, 6B, and 9A  is open at both ends. Alternatively, or additionally, either end, or both ends, of the filter or filter element, can include fittings, for example, the embodiments shown in  FIGS. 7A, 8A, 8B, and 9A  show fittings  700 , e.g., NPT  701 , and venture fitting  702  ( FIG. 9A ). 
     Typically, using  FIG. 2D  for general reference, consecutive portions have center to center (X) distances in the range of from about 0.02 inches to about 2 inches (about 0.05 cm to about 5.1 cm). 
     Typically, using  FIG. 4  for general reference, the depth (D) of a portion can be in the range of from about 0.01 inches to about 2.40 inches (about 0.03 cm to about 6.1 cm), and the typical height (H) of a portion can be in the range of from about 0.03 inches to about 55 inches (about 0.08 cm to about 140 cm). A ratio of height to depth in accordance with an embodiment of the invention is typically in the range of about 1:1 to about 10:1, preferably in the range of from about 1:1 to about 2:1, in some embodiments, about 1.3:1. 
     Typically, using  FIG. 5  for general reference, spacing between portions on adjacent pleats can be spaced at an angle (Y) in the range of about 0.9° to about 180° with respect to the center of the filter element. 
     Typically, the width of a portion can be in the range of from about 0.03 inches to about 5 inches (about 0.08 cm to about 12.7 cm). 
     Typically, the number of rows of pleats in each element is in the range of 2 rows to about 3700 rows. 
     Typically, the outer diameter of the filter element is in the range of about 0.2 inches to about 5 inches (about 0.05 cm to about 12.7 cm); typically, the inner diameter of the filter element is in the range of about 0.2 inches to about 5 inches (about 0.51 cm to about 12.7 cm). 
     Typically, the element wall thickness is in the range of from about 0.01 inches to about 0.12 inches (about 0.03 cm to about 0.30 cm). 
     Typically, filter elements have lengths in the range of from about 2 inches to about 120 inches (about 5.1 cm to about 305 cm) and/or external diameters in the range of about 0.2 inches to about 5 inches (about 0.51 cm to about 12.7 cm). 
     The filter elements, pleats, portions, and end caps (if present, and if porous) can have any suitable pore structure, e.g., a pore size (for example, as evidenced by bubble point, or by K L  as described in, for example, U.S. Pat. No. 4,340,479, or evidenced by capillary condensation flow porometry), a mean flow pore (MFP) size (e.g., when characterized using a porometer, for example, a Porvair Porometer (Porvair plc, Norfolk, UK), or a porometer available under the trademark POROLUX (Porometer.com; Belgium)), a pore rating, a pore diameter (e.g., when characterized using the modified OSU F2 test as described in, for example, U.S. Pat. No. 4,925,572), or removal rating media. The pore structure used depends on the size of the particles to be utilized, the composition of the fluid to be treated, and the desired effluent level of the treated fluid. 
     Typically, in accordance with some embodiments of the invention, the porous elements, pleats, and portions, each have a pore size in the range of from about 2 micrometers (μm) to about 70 micrometers. 
     The particles used to produce the filters and filter elements can comprise a variety of metal powders, and filters and filter elements can be, for or example, formed from stainless steel powder, such as 316 low-carbon stainless steel and 310 stainless steel, by a process including sintering. Other suitable metal powders include, for example, alloys (e.g., HASTELLOY® X, and HAYNES® HR-160® (Haynes International); and Inconel 600), nickel, chromium, tungsten, copper, bronze, aluminum, platinum, iron, magnesium, cobalt, or a combination (including a combination of metals and metal alloys) thereof. 
     The particles can be any suitable size, and filters and filter elements can include a distribution of particle sizes. The size(s) of the particles for a particular application is related to the desired pore size in the finished filter and filter element. 
     The hollow filter element can have any suitable inner and outer diameter and length. 
     Preferably, the filter and filter elements are sterilizable, illustratively, able to be cleaned in place (CIP) via, for example, steam sterilization or chemical sterilization. 
     Filter elements according to embodiments of the invention are preferably monolithic, preferably manufactured via additive manufacturing (sometimes referred to as “additive layer manufacturing” or “3D printing”). They are typically formed by repeated depositions of a metal powder bound together with an activatable binder (e.g., binder jetting, sometimes referred to as “drop on powder”), typically followed by agglomerating the powder, e.g., by sintering. The end caps (if present) and filter elements can be manufactured together via additive manufacturing in a continuous operation at substantially the same time. 
     Any suitable additive manufacturing equipment can be used, and a variety of production 3D printers are suitable and commercially available. 
       FIGS. 10A-10C  shown an illustrative filter system according to an embodiment of the invention. The illustrated embodiment of the filter system (sometimes referred to as a tubesheet/filter bundle)  2000  comprises a plurality of filters  1000  arranged vertically (wherein  1700  in  FIGS. 10B and 10C  reflects the outer diameter of the tube sheet), the system typically comprising a feed for fluid (e.g., liquid or gas) to be filtered, and a discharge channel for filtered liquid or gas. In the illustrated embodiment, the filter system comprises a lower grid plate  1701 , and plurality of modules  1500 A,  1500 B,  1500 C, with respective inlet piping for back pulse gas channels  1510 A,  1510 B,  1510 C, each module comprising a plurality of filters  1000 . A feed channel (not shown) for raw liquid (e.g., raw gas) would be located in a housing shell. 
     Typically, the housing can be divided into raw gas chamber receiving the gas to be filtered, and a clean gas chamber for the filtered gas. 
     Preferably, embodiments of the system are arranged to allow reverse-flushing (back-pulsing), followed by filtration, without removing the filters or modules from a housing.  FIGS. 10A and 10B  show a reverse-flushing system  1950  comprising back-pulsing channels  1900 A,  1900 B, and  1900 C. If desired, the reverse-flushing system can include a pressure source. 
     The particulate matter discharged during reverse-flushing is preferably collected by gravity in dust collectors arranged at the bottom of the housing, outside of the housing. The filters or modules are arranged (e.g., by staggering when reverse-flushing) such that, upon reverse-flushing, when particulate matter is detached from the filter elements, no cross-contamination between neighboring filters or filter modules can occur. 
     The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope. 
     EXAMPLE 1 
     This example demonstrates the improvement in area per unit length of filter elements according to an embodiment of the invention compared to commercially available cylindrical filters. 
     Filter elements are produced with one tapered end and one blind end. 1″ (2.54 cm) NPT fittings are welded onto three filter elements to test them simultaneously and compared to 3 commercially available hollow cylindrical filter elements that have areas corresponding to the produced filter elements. The 3 sets of areas are 0.8 actual liter per minute/square inch (alpm/in 2 ); 1.04 alpm/in 2 , and 1.46 alpm/in 2 . 
     While both sets of filter elements have the same area and inner and outer diameters, the commercially available filters are twice as long as the filter elements according to embodiments of the invention. 
     The differential pressures (delta P&#39;s) for the commercially available filters are 0.243 psi, 0.335 psi, and 0.491 psi, respectively, and the delta P&#39;s for the embodiments of the invention are 0.226 psi, 0.307 psi, and 0.516 psi. 
     The example shows that embodiments of the invention have more area per unit length than the commercially available filters while exhibiting comparable delta P&#39;s. 
     EXAMPLE 2 
     This example demonstrates additional advantages in the improvement in area per unit length of filter elements according to an embodiment of the invention compared to commercially available cylindrical filters. 
     Simulated blowback testing of the filter elements as described in Example 1 is carried out with a low inlet face velocity of the 0.8 alpm/in 2  filter elements, a medium inlet face velocity with the 1.04 alpm/in 2  filter elements, and a high inlet face velocity with the 1.46 alpm/in 2  filters. 
     The stable delta P&#39;s for the commercially available filters are 0.243 psi, 0.335 psi, and 0.491 psi, and the stable delta P&#39;s for the embodiments of the invention are 0.226 psi, 0.307 psi, and 0.516 psi. 
     EXAMPLE 3 
     This example demonstrates additional advantages in the improvement in area per unit length of filter elements according to an embodiment of the invention compared to commercially available cylindrical filters. 
     This test is performed by comparing embodiments of the invention that are half the length, but the same area as the commercially available filters. 
     Simulated blowback testing of the filter elements as described in Example 1 is carried out with the same system inlet flow using the same 3 sets of filter elements. The stable delta P&#39;s for the commercially available filters are 0.491 psi, and for embodiments of the invention are 0.226 psi. This shows that for embodiments of filter elements according to the invention having the same length as commercially available filter elements, the stable delta P&#39;s for embodiments of the invention would be about half that of commercially available filter elements. 
     EXAMPLE 4 
     This example demonstrates improvement in dirt capacity of a filter element according to an embodiment of the invention compared to a commercially available cylindrical filter. 
     A filter element according to an embodiment of the invention is produced as in example 1, and a 10″ long commercially available cylindrical filter element is obtained. The filter elements have essentially the same area. 
     The dirt capacity of the commercially available filter element is 2.7 g, and the dirt holding capacity (DHC) is 6.1 g/ft 2 , whereas the dirt capacity of the filter element according to an embodiment of the invention is 4.5 g, and the DHC is 5.0 g/ft 2 . Since the DHC is normalized per unit area, the important comparison is dirt capacity. 
     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 “at least one” 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. The use of the term “at least one” followed by a list of one or more items (for example, “at least one of A and B”) is to be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B), 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. 
     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.