Patent Description:
<CIT> discloses a pleated media pack including a section of media configured into a tube defining an interior volume and an open opening at one end. A ratio of the pleat depth to a diameter of the opening is greater than <NUM>. At least some of the pleats at one end of the media pack are inverted. In some examples, the pleats include major pleats alternating with minor pleats.

<CIT> relates to a filter element for a precoat filter having a septum formed with longitudinal pleats having broad roots proximal to a perforate core and narrow tips distal from the core. The filter element may include circumferential supporting bands spaced axially along the filter element and constraining the septum tips. In use a deposit of mechanical or ion exchange precoat is applied to the element before filtering and later removed by backwashing.

<CIT> discloses a filter element having a pleated composite and first and second end elements mounted to opposite first and second ends of the filter element. The pleated composite has a filter medium layer and a grooved mesh drainage layer pleated with the filter medium layer. The grooved mesh drainage layer has a plurality of strands and a plurality of grooves formed in the strands. The grooved mesh drainage layer directs fluid via the grooves to or from the filter medium layer and the filter medium layer removes one or more substances from fluid flowing through the filter medium layer.

US patent <CIT> relates to a disposable filter cartridge including an outer perforated shell, a paper filter element located within the shell including a plurality of pleated portions. Each of the pleated portions including a radial outer edge, each of the outer radial edges including a plurality of radially inwardly directed indentations at spaced apart points thereon, the indentations being aligned circumferentially and in abutting relationship to form a surface for disposing a filter reinforcing adhesive and to space adjacent pleats apart from one another to form inlets to the filter element.

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.

The invention provides a porous filter element as defined in claim <NUM>. The filter element comprises 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 H to width W aspect ratio, wherein the height H is about equal to or larger than the width W.

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.

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 H to width W aspect ratio, wherein the height H is about equal to or larger than the width W. In a typical embodiment, the height H to width W aspect ratio is larger than <NUM>, preferably the height H is at least <NUM> times larger than the width W, in some embodiments the height H is at least <NUM> times larger than the width W.

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 <NUM> elements, at least <NUM> 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 <NUM>) 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>). 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 <NUM> times (in preferred embodiments, at least about <NUM> 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 <NUM>,<NUM> blowback cycles and over <NUM>,<NUM> 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 <FIG> and <FIG>, a filter <NUM> comprises a porous filter element <NUM> comprising a hollow cylindrical porous metal medium <NUM> having a hollow interior <NUM> including an interior surface 55A defining the hollow interior, a first end <NUM>, and a second end <NUM>. The filter element includes a plurality of pleats <NUM> longitudinally arranged along an axis A from the first end to the second end, each pleat comprising a plurality of portions <NUM> having a height H to width W aspect ratio, wherein the height H is equal to or larger than the width W. Typically, when viewed from the side (e.g., as shown in <FIG>), the top surfaces 150A 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 <NUM>. 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 <FIG>), the top surface 175A of the bridge is lower than the top surface 150A of the portions.

As shown in <FIG>, <FIG> the interior surface 55A includes concave openings <NUM>, communicating with hollow interiors <NUM> of each portion, the portions being closed at the top (covered by top surfaces 150A).

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>, the end <NUM> of the filter element has a taper 51A, such that the depth of the portions <NUM>'at the end flares out to meet the outside diameter <NUM>' 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. <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, and <FIG> show an end cap <NUM>. In the embodiment illustrated in <FIG>, <FIG>, <FIG>, <FIG>, <FIG>, and <FIG>, porous filter element <NUM> is closed at one end with an end cap, porous filter element 500A as illustrated in <FIG>, <FIG>, and <FIG> 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 <FIG>, <FIG>, <FIG>, and <FIG> show fittings <NUM>, e.g., NPT <NUM>, and venture fitting <NUM> (<FIG>).

Typically, using <FIG> for general reference, consecutive portions have center to center (X) distances in the range of from about. <NUM> to about <NUM> (about. <NUM> inches to about <NUM> inches).

Typically, using <FIG> for general reference, the depth (D) of a portion can be in the range of from about. <NUM> to about <NUM> (about. <NUM> inches to about <NUM> inches), and the typical height (H) of a portion can be in the range of from about. <NUM> to about <NUM> (about. <NUM> inches to about <NUM> inches). A ratio of height to depth in accordance with an embodiment of the invention is typically in the range of about <NUM>:<NUM> to about <NUM>:<NUM>, preferably in the range of from about <NUM>:<NUM> to about <NUM>: <NUM>, in some embodiments, about <NUM>:<NUM>.

Typically, using <FIG> for general reference, spacing between portions on adjacent pleats can be spaced at an angle (Y) in the range of about <NUM>° to about <NUM>° with respect to the center of the filter element.

Typically, the width of a portion can be in the range of from about. <NUM> to about <NUM> (about. <NUM> inches to about <NUM> inches).

Typically, the number of rows of pleats in each element is in the range of <NUM> rows to about <NUM> rows.

Typically, the outer diameter of the filter element is in the range of about. <NUM> to about <NUM> (about. <NUM> inches to about <NUM> inches); typically, the inner diameter of the filter element is in the range of about. <NUM> to about <NUM> (about. <NUM> inches to about <NUM> inches).

Typically, the element wall thickness is in the range of from about. <NUM> to about. <NUM> (about <NUM> inches to about <NUM> inches).

Typically, filter elements have lengths in the range of from about <NUM> to about <NUM> (about <NUM> inches to about <NUM> inches) and/or external diameters in the range of about. <NUM> to about <NUM> (about <NUM> inches to about <NUM> inches).

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 KL as described in, for example, <CIT>, 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, <CIT>), 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 <NUM> micrometers (µm) to about <NUM> 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 <NUM> low-carbon stainless steel and <NUM> stainless steel, by a process including sintering. Other suitable metal powders include, for example, alloys (e.g., HASTELLOY® X, and HAYNES® HR-<NUM>® (Haynes International); and Inconel <NUM>), 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.

<FIG> 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) <NUM> comprises a plurality of filters <NUM> arranged vertically (wherein <NUM> in <FIG> 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 <NUM>, and plurality of modules 1500A, 1500B, 1500C, with respective inlet piping for back pulse gas channels 1510A, 1510B, 1510C, each module comprising a plurality of filters <NUM>. 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. <FIG> and <FIG> show a reverse-flushing system <NUM> comprising back-pulsing channels 1900A, 1900B, and 1900C. 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.

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. <NUM> (<NUM>") NPT fittings are welded onto three filter elements to test them simultaneously and compared to <NUM> commercially available hollow cylindrical filter elements that have areas corresponding to the produced filter elements. The <NUM> sets of areas are <NUM> actual liter per minute/cm<NUM> (alpm/cm<NUM>); <NUM> alpm/cm<NUM> and <NUM> alpm/cm<NUM> (<NUM> actual liter per minute/square inch (alpm/in<NUM>); <NUM> alpm/in<NUM>, and <NUM> alpm/in<NUM>).

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's) for the commercially available filters are <NUM> kPa, <NUM> kPa, and <NUM> kPa (<NUM> psi, <NUM> psi, and <NUM> psi), respectively, and the delta P's for the embodiments of the invention are <NUM> kPa, <NUM> kPa, and <NUM> kPa (<NUM> psi, <NUM> psi, and <NUM> 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's.

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 <NUM> is carried out with a low inlet face velocity of the <NUM> alpm/cm<NUM> (<NUM> alpm/in<NUM>) filter elements, a medium inlet face velocity with the <NUM> alpm/cm<NUM> (<NUM> alpm/in<NUM>) filter elements, and a high inlet face velocity with the <NUM> alpm/cm<NUM> (<NUM> alpm/in<NUM>) filters.

The stable delta P's for the commercially available filters are <NUM> kPa, <NUM> kPa, and <NUM> kPa (<NUM> psi, <NUM> psi, and <NUM> psi), and the stable delta P's for the embodiments of the invention are <NUM> kPa, <NUM> kPa, and <NUM> kPa (<NUM> psi, <NUM> psi, and <NUM> psi).

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 <NUM> is carried out with the same system inlet flow using the same <NUM> sets of filter elements. The stable delta P's for the commercially available filters are <NUM> kPa (<NUM> psi), and for embodiments of the invention are <NUM> kPa (<NUM> 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's for embodiments of the invention would be about half that of commercially available filter elements.

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 <NUM>, and a <NUM> (<NUM>") 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 <NUM>, and the dirt holding capacity (DHC) is <NUM>/m<NUM> (<NUM>/ft<NUM>), whereas the dirt capacity of the filter element according to an embodiment of the invention is <NUM>, and the DHC is <NUM>/m<NUM> (<NUM>/ft<NUM>). Since the DHC is normalized per unit area, the important comparison is dirt capacity.

Claim 1:
A porous filter element (<NUM>) comprising a hollow cylindrical porous metal medium (<NUM>) having a first end and a second end (<NUM>; <NUM>), the hollow cylindrical porous metal medium (<NUM>) comprising a plurality of pleats (<NUM>) longitudinally arranged along an axis A from the first end to the second end (<NUM>; <NUM>) of the hollow cylindrical porous metal medium (<NUM>), each pleat (<NUM>) comprising a plurality of portions (<NUM>), said portions (<NUM>) having a height H extending parallel to said axis A and a width W perpendicular to said height H, each portion (<NUM>) having a height H to width W aspect ratio, wherein the height H is equal to or larger than the width W, and
wherein there is a gap between consecutive portions (<NUM>) or the consecutive portions (<NUM>) are connected by a bridge (<NUM>).