EP4689277A1

EP4689277A1 - Level controlled separator for foam forming

Info

Publication number: EP4689277A1
Application number: EP24781815.6A
Authority: EP
Inventors: Stephen A. Marrano; Kyle KRAUTKRAMER; Peter Wallace
Original assignee: Kimberly Clark Worldwide Inc; Kimberly Clark Corp
Current assignee: Kimberly Clark Worldwide Inc; Kimberly Clark Corp
Priority date: 2023-03-29
Filing date: 2024-03-27
Publication date: 2026-02-11
Also published as: CN121263571A; WO2024206443A1; KR20250163972A; AU2024249166A1; MX2025011433A

Abstract

A process and system for foam forming webs is disclosed. A foamed suspension of materials, such as fibers and other particles, is fed to one or more forming zones that are sequentially positioned along an inclined forming surface. A plurality of corresponding drain devices are positioned below the forming surface for draining excess fluids from the newly formed web. The flow rate of fluids being drained from the web is controlled in relation to the flow rate or pressure of a foamed suspension of fibers fed to the forming zones.

Description

LEVEL CONTROLLED SEPARATOR FOR FOAM FORMING

BACKGROUND

Many tissue products, such as facial tissue, bath tissue, paper towels, industrial wipers, and the like, are produced according to a wet laid process. Wet laid webs are made by depositing an aqueous suspension of pulp fibers onto a forming fabric and then removing water from the newly- formed web.

In order to improve various characteristics of tissue webs, webs have also been formed according to a foam forming process. During a foam forming process, a foamed suspension of fibers is created and spread onto a moving porous conveyor for producing an embryonic web. Foam formed webs can demonstrate improvements in bulk, stretch, caliper, and/or absorbency. In addition to tissue webs, foam forming can be used to make all different types of webs and products. For example, relatively long fibers and synthetic fibers can be incorporated into webs using a foam forming process. Thus, foam forming processes can be more versatile than many wet laid processes.

In certain conventional foam forming systems, one or more fan pumps flow foam from a separation silo to a backwater tank through a short race. Such arrangement can have drawbacks. For instance, large fan pumps and/or vacuum assistance may be required to provide sufficient suction pressure of the low-density form in the separation silo. As another example, the compressibility of the foam in the separator silo can limit the vacuum applicable at the separation silo.

A system for improved foam handling between a separation silo to a backwater tank would be useful.

SUMMARY

In general, the present disclosure is directed to an improved process and system for flowing foam between a separator and a tank. A pump is operable to flow foam from the separator to the tank. The pump may be controlled to maintain a level of foam in the separator based on a signal from a sensor that detects the level of the foam in the separator. The processes and systems of the present disclosure can advantageously assist with reducing or preventing over-draining or under-draining of foam from the separator. Moreover, over-draining foam from the separator can entrain large air bubbles into the flow of foam from the separator, which can decrease foam density and impede foam flow. In contrast, under-draining foam from the separator can loss of vacuum in the separator, frothing of foam in the separator, and introduce foam into a vacuum source. Such negative effects of overdraining and under-draining can be limited or prevented by operating the pump to maintain the level of foam in the separator. The processes and systems of the present disclosure can also advantageously assist with providing a consistent residence time for foam in the separator, which can improve foam stability.

In one example embodiment, a foam forming system includes a headbox and a tank. A separator is disposed between the headbox and the tank along a flow path for foam between the headbox and the tank. The separator includes an inlet for the foam, a first outlet for the foam, and a second outlet for free air from the foam. The foam forming system also includes a pump. A sensor is operable to determine a level of the foam in the separator. A controller is configured to receive a signal from the sensor corresponding to the level of the foam in the separator and, based at least in part on the level of the foam in the separator, operate the pump to maintain the level of the foam within a determined range within the separator.

In another example embodiment, a foam forming system includes a tank. A vacuum separator includes an inlet for foam, a first outlet for the foam, and a second outlet for free air from the foam. The vacuum separator is coupled to the tank via the first outlet such that the foam is flowable from the vacuum separator to the tank. A pump is operable to flow the foam from the vacuum separator to the tank. A sensor is operable to determine a level of the foam in the vacuum separator. A controller is configured to determine the level of the foam in the vacuum separator based at least in part on a signal from the sensor and operate the pump to maintain the level of the foam within a determined range within the vacuum separator based at least in part on the determined level of the foam in the vacuum separator.

In another example embodiment, a method for foam forming includes: flowing foam from a headbox to a vacuum separator; flowing free air from the foam out of the vacuum separator through a vacuum outlet of the vacuum separator; and operating a pump to flow the foam out of the vacuum separator through a foam outlet of the vacuum separator. Operating the pump includes determining a level of the foam in the vacuum separator with a sensor and adjusting a flow rate of the pump to maintain the level of the foam within a determined range within the vacuum separator based at least in part on the determined level of the foam in the vacuum separator.

Other features and aspects of the present disclosure are discussed in greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present disclosure is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

FIG. 1 is a schematic view of a system and process according to an example embodiment of the present disclosure for forming webs from a foamed suspension of materials; FIG. 2 is a schematic view of a system and process according to an example embodiment of the present disclosure for depositing a foamed suspension of materials onto a forming surface in accordance with the present disclosure; and

FIG. 3 is a schematic view of a system and process according to an example embodiment of the present disclosure for separating free air from a flow of foam during foam forming of a non-woven web.

FIG. 4 is a flow diagram of a process according to an example embodiment of the present disclosure for separating free air from a flow of foam during foam forming of a non-woven web.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

DEFINITIONS

When introducing elements of the present disclosure or the preferred embodiment(s) thereof, the articles “a”, "an”, "the” and "said” are intended to mean that there are one or more of the elements. As used herein, the terms “includes” and “including” are intended to be inclusive in a manner similar to the term “comprising.” Similarly, the term “or” is generally intended to be inclusive (i.e. , “A or B" is intended to mean “A or B or both”). Approximating language, as used herein throughout the specification and claims, is applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately,” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. For example, the approximating language may refer to being within a ten percent (10%) margin.

As used herein, the term “foam formed product” means a product formed from a suspension including a mixture of a solid, a liquid, and dispersed gas bubbles.

As used herein, the term “foam forming process” means a process for manufacturing a product involving a suspension including a mixture of a solid, a liquid, and dispersed gas bubbles.

As used herein, the term “foaming fluid” means any one or more known fluids compatible with the other components in the foam forming process. Suitable foaming fluids include, but are not limited to, water.

As used herein, the term “foam half life” means the time elapsed until the half of the initial foam mass reverts to liquid water. As used herein, the term “layer" refers to a structure that provides an area of a substrate in a height direction of the substrate that is comprised of similar components and structure.

As used herein, the term "nonwoven web" means a web having a structure of individual fibers or threads which are interlaid, but not in an identifiable manner as in a knitted web.

As used herein, unless expressly indicated otherwise, when used in relation to material compositions the terms "percent", “%”, "weight percent", or "percent by weight" each refer to the quantity by weight of a component as a percentage of the total except as whether expressly noted otherwise.

The term “personal care absorbent article” refers herein to an article intended and/or adapted to be placed against or in proximity to the body (i.e., contiguous with the body) of the wearer to absorb and contain various liquid, solid, and semi-solid exudates discharged from the body. Examples include, but are not limited to, diapers, diaper pants, training pants, youth pants, swim pants, feminine hygiene products, including, but not limited to, menstrual pads or pants, incontinence products, medical garments, surgical pads and bandages, and so forth.

The term "superabsorbent material" as used herein refers to water-swellable, water-insoluble organic or inorganic materials including superabsorbent polymers and superabsorbent polymer compositions capable, under the most favorable conditions, of absorbing at least about ten times (1 OX) their weight, or at least about fifteen times (15X) their weight, or at least about twenty-five times (25X) their weight in an aqueous solution containing nine-tenths (0.9) weight percent sodium chloride.

The term "machine direction" as used herein refers to the direction of travel of the forming surface onto which fibers are deposited during formation of a nonwoven web.

The term "cross-machine direction" as used herein refers to the direction which is perpendicular to the machine direction defined above.

The term "pulp" as used herein refers to fibers from natural sources such as woody and non- woody plants. Woody plants include, for example, deciduous and coniferous trees. Non-woody plants include, for example, cotton, flax, esparto grass, milkweed, straw, jute, hemp, and bagasse. Pulp fibers may include hardwood fibers, softwood fibers, and mixtures thereof.

The term "average fiber length" as used herein refers to an average length of fibers, fiber bundles and/or fiber-like materials determined by measurement utilizing microscopic techniques. A sample of at least 20 randomly selected fibers is separated from a liquid suspension of fibers. The fibers are set up on a microscope slide prepared to suspend the fibers in water. A tinting dye is added to the suspended fibers to color cellulose-contain Ing fibers so they may be distinguished or separated from synthetic fibers. The slide is placed under a Fisher Stereomaster II Microscope-S19642/S19643 Series. Measurements of 20 fibers in the sample are made at 20X linear magnification utilizing a 0-20 mils scale and an average length, minimum and maximum length, and a deviation or coefficient of variation are calculated. In some cases, the average fiber length will be calculated as a weighted average length of fibers (e.g . , fibers, fiber bundles, fiber-like materials) determined by equipment such as, for example, a Kajaani fiber analyzer Model No. FS-200, available from Kajaani Oy Electronics, Kajaani, Finland. According to a standard test procedure, a sample is treated with a macerating liquid to ensure that no fiber bundles or shives are present. Each sample is disintegrated into hot water and diluted to an approximately 0.001% suspension. Individual test samples are drawn in approximately 50 to 100 ml portions from the dilute suspension when tested using the standard Kajaani fiber analysis test procedure. The weighted average fiber length may be an arithmetic average, a length weighted average or a weight weighted average and may be expressed by the following equation: where k=maximum fiber length xrfiber length n₍-number of fibers having length xi n=total number of fibers measured.

One characteristic of the average fiber length data measured by the Kajaani fiber analyzer is that it does not discriminate between different types of fibers. Thus, the average length represents an average based on lengths of all different types, if any, of fibers in the sample.

As used herein the term "staple fibers” means discontinuous fibers made from synthetic polymers such as polypropylene, polyester, post consumer recycle (FOR) fibers, polyester, nylon, and the like, and those not hydrophilic may be treated to be hydrophilic. Staple fibers may be cut fibers or the like. Staple fibers can have cross-sections that are round, bicomponent, multicomponent, shaped, hollow, or the like.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present disclosure. In general, the present disclosure is directed to a system and method for foam forming a nonwoven web. In the system, a separator silo is separate from a backwater tank, and a pump may be configured to flow foam from the separator silo to the backwater tank. The pump may be controlled to maintain a consistent level range for the foam in the separator silo. Moreover, the level of the foam in the separator silo can be measured by a sensor, such as a capacitive rod, and the pump may be controlled based upon sensor measurements. The separator silo may be configured to operate under vacuum, and the backwater tank may be configured at ambient pressure.

The system and process of the present disclosure can provide various advantages and benefits. For instance, the system may include a fan pump that is separate from the pump and configured to urge the foam from the backwater tank to a headbox. The fan pump may operate with increased efficiency and robustness by utilizing the pump to maintain the consistent level range for the foam in the separator silo. Thus, a suction head for the fan pump may be improved and/or a centrifugal pump may be used at the fan pump rather than a vacuum assisted centrifugal pump. As another example, a vacuum level within the overall system may be increased, and the desired vacuum level may be decoupled from a machine height. Thus, a height differential between a free surface of the foam in the separator silo and a free surface of the foam in the backwater tank may be substantially reduced by utilizing the pump to maintain the consistent level range for the foam in the separator silo. As another example, utilizing the pump to maintain the consistent level range for the foam in the separator silo may assist with reducing or preventing over-draining or under-draining of foam from the separator silo. Thus, entrainment of large air bubbles into the flow of foam from the separator silo may be avoided and/or introduction of foam into a vacuum source for the separator silo may be avoided. As another example, utilizing the pump to maintain the consistent level range for the foam in the separator silo may assist with providing a consistent residence time for foam in the separator, which can improve foam stability.

Referring to FIGS. 1 and 2, an example embodiment of a system and process in accordance with aspects of the present disclosure is shown. In general, during the process, solid material, such as fibers and/or superabsorbent particles, water, and a foam forming agent are added to a tank and mixed until the desired air content, bubble size/foam stability, and solid dispersion are achieved, such as a fiber dispersion. The fiber-containing foam may then optionally be diluted during the process, especially when a recycle stream is present. In one example aspect, the air content of the foamed suspension is between about thirty percent (30%) and about sixty-five percent (65%). As will be described below, example aspects of the process and system of the present disclosure are directed to separating foam from free air and managing foam, e.g., during foam forming of a nonwoven web. FIG. 1 illustrates a system and process for producing a foamed suspension of fibers and for forming webs from the foamed suspension of fibers. It will be understood that the example system shown in FIG. 1 is provided by way of example and that any suitable web forming system may be used in accordance with the present disclosure. As shown in FIG. 1 , the system may include a mixing tank 12 configured to form the foamed suspension of fibers. The foamed suspension of fibers may then be fed to a headbox or web forming system 10 that deposits the foamed suspension of fibers onto a porous forming surface 26 for forming a web 14. The mixing tank 12 may be in communication with a water supply 22 for feeding water to the tank and a foaming agent or surfactant supply 24 for feeding a surfactant to the tank 12. A fiber furnish may also be fed to the tank 12 and combined with the water and surfactant. The aqueous solution formed by combining the surfactant and water may be agitated and formed into a foam for forming a foamed suspension of fibers. As described above, in addition to fibers, various other materials may be combined in the tank 12. Such other materials, for instance, may include superabsorbent particles or the like.

The surfactant or foaming agent, for instance, may include any suitable surfactant. In one example embodiment, for instance, the foaming agent may include sodium lauryl sulfate, which is also known as sodium laureth sulfate or sodium lauryl ether sulfate. Other foaming agents include sodium dodecyl sulfate or ammonium lauryl sulfate. In other example embodiments, the foaming agent may include any suitable cationic and/or amphoteric surfactant. For instance, other foaming agents include fatty acid amines, amides, amine oxides, fatty acid quaternary compounds, and the like. In one example embodiment, a nonionic surfactant is used. The nonionic surfactant, for instance, may include an alkyl polyglycoside. In one aspect, for instance, the surfactant may be a C8 alkyl polyglycoside, a C10 alkyl polyglycoside, or a mixture of C8 and C10 alkyl polyglycosides.

The foaming agent may be combined with water generally in an amount greater than about one-tenth of a percent (0.1%) by weight, such as in an amount greater than about half of a percent (0.5%) by weight, such as in an amount greater than about seven-tenths of a percent (0.7%) by weight. One or more foaming agents may generally be present in an amount of from about one- hundredth of a percent (0.01 %) by weight to about five percent (5%) by weight, such as in an amount up to about two percent (2%) by weight.

When the foaming agent and water are combined, the mixture may be blended or otherwise subjected to forces capable of forming a foam. A foam generally refers is an aggregate of hollow cells or bubbles.

The foam density can vary depending upon the particular application and various factors including the fiber furnish used. In one example embodiment, for instance, the foam density of the foam may be greater than about two hundred grams per liter (200 g/L), such as greater than about two hundred and fifty grams per liter (250 g/L), such as greater than about three hundred grams per liter (300 g/L). The foam density is generally less than about six hundred grams per liter (600 g/L), such as less than about five hundred grams per liter (500 g/L), such as less than about four hundred grams per liter (400 g/L), such as less than about three hundred and fifty grams per liter (350 g/L). In one example embodiment, for instance, a lower density foam is used having a foam density of generally less than about three hundred and fifty grams per liter (350 g/L), such as less than about three hundred and forty grams per liter (340 g/L) , such as less than about three hundred and thirty grams per liter (330 g/L). The foam may generally have an air content of greater than about forty percent (40%), such as greater than about fifty percent (50%), such as greater than about sixty percent (60%), e.g. , at standard temperature and pressure (STP). The air content is generally less than about seventy-five percent (75%) by volume, such as less than about seventy percent (70%) by volume, such as less than about sixty-five percent (65%) by volume.

The foam may be formed in the presence of a fiber furnish or, alternatively, the foam may first be formed and then combined with a fiber furnish. In general, any fibers capable of making a basesheet, such as a tissue web or other similar type of nonwoven, may be used.

Fibers suitable for making webs include any natural or synthetic cellulosic fibers including, but not limited to: nonwoody fibers, such as cotton, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and woody or pulp fibers, such as those obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers; hardwood fibers, such as eucalyptus, maple, birch, and aspen. Pulp fibers may be prepared in high-yield or low-yield forms and may be pulped in any known method, including kraft, sulfite, high-yield pulping methods and other known pulping methods. Fibers prepared from organosolv pulping methods may also be used.

A portion of the fibers, such as up to one hundred percent (100%) or less by dry weight, or from about five percent (5%) to about thirty percent (30%) by dry weight, may be synthetic fibers, such as rayon, polyolefin fibers, polyester fibers, bicomponent sheath-core fibers, multi-component binder fibers, and the like. The fibers may be virgin fibers or recycled fibers. The fibers may be staple fibers and may have an average length of from about three millimeters (3 mm) to about one hundred and fifty millimeters (150 mm). An exemplary polyethylene fiber is Fybrel®, available from Minifibers, Inc. (Jackson City, Tenn.). When containing synthetic polymer fibers, the web may be thermally bonded where the fibers intersect.

Synthetic cellulose fiber types include rayon in all its varieties and other fibers derived from viscose or chemically-modified cellulose. Chemically treated natural cellulosic fibers may be used, such as mercerized pulps, chemically stiffened or crosslinked fibers, or sulfonated fibers. For good mechanical properties in using papermaking fibers, it may be desirable that the fibers be relatively undamaged and largely unrefined or only lightly refined. While recycled fibers may be used, virgin fibers are generally useful for their mechanical properties and lack of contaminants. Mercerized fibers, regenerated cellulosic fibers, cellulose produced by microbes, rayon, and other cellulosic material or cellulosic derivatives may be used. Suitable papermaking fibers may also include recycled fibers, virgin fibers, or mixes thereof. In certain example embodiments capable of high bulk and good compressive properties, the fibers may have a Canadian Standard Freeness of at least two hundred (200), more specifically at least three hundred (300), more specifically still at least four hundred (400), and most specifically at least five hundred (500).

Other papermaking fibers that may be used include paper broke or recycled fibers and high yield fibers. High yield pulp fibers are those papermaking fibers produced by pulping processes providing a yield of about sixty-five percent (65%) or greater, more specifically about seventy-five percent (75%) or greater, and still more specifically about seventy-five percent (75%) to about ninety- five percent (95%). Yield is the resulting amount of processed fibers expressed as a percentage of the initial wood mass. Such pulping processes include bleached chemithermomechanical pulp (BCTMP), chemithermomechanical pulp (CTMP), pressure/pressure thermomechanical pulp (PTMP), thermomechanical pulp (TMP), thermomechanical chemical pulp (TMCP), high yield sulfite pulps, and high yield Kraft pulps, all of which leave the resulting fibers with high levels of lignin. High yield fibers are well known for their stiffness in both dry and wet states relative to typical chemically pulped fibers.

The web may also be formed without a substantial amount of inner fi ber-to-fi ber bond strength. In this regard, the fiber furnish used to form the base web may be treated with a chemical debonding agent. The debonding agent may be added to the foamed fiber slurry during the pulping process or may be added directly to the headbox. Suitable debonding agents that may be used include cationic debonding agents, such as fatty dialkyl quaternary amine salts, mono fatty alkyl tertiary amine salts, primary amine salts, imidazoline quaternary salts, silicone quaternary salt and unsaturated fatty alkyl amine salts. Other suitable debonding agents are disclosed in U.S. Pat. No. 5,529,665 to Kaun, the entirety of which is incorporated herein by reference. In particular, Kaun discloses the use of cationic silicone compositions as debonding agents.

In one example embodiment, the debonding agent used in the process of the present disclosure may be an organic quaternary ammonium chloride and, particularly, a silicone-based amine salt of a quaternary ammonium chloride. For example, the debonding agent may be PROSOFT.RTM. TQ1003, marketed by the Hercules Corporation. The debonding agent may be added to the fiber slurry in an amount of from about one kilogram per metric ton (1 kg/tonne) to about ten kilograms per metric ton (10 kg/tonne) of fibers present within the slurry.

In an alternative example embodiment, the debonding agent may be an imidazoline-based agent. The imidazoline-based debonding agent may be obtained, for instance, from the Witco Corporation. The imidazoline-based debonding agent may be added in an amount of between two kilograms per metric ton (2.0 kg/tonne) to about fifteen kilograms per metric ton (15 kg/tonne).

Other optional chemical additives may also be added to the aqueous papermaking furnish or to the formed embryonic web to impart additional benefits to the product and process. The following materials are included as examples of additional chemicals that may be applied to the web. The chemicals are included as examples and are not intended to limit the scope of the disclosure. Such chemicals may be added at any point in the papermaking process.

Additional types of chemicals that may be added to the paper web include, but are not limited to, absorbency aids usually in the form of cationic, anionic, or non-ionic surfactants, humectants and plasticizers, such as low molecular weight polyethylene glycols, and polyhydroxy compounds, such as glycerin and propylene glycol. Materials that supply skin health benefits, such as mineral oil, aloe extract, vitamin E, silicone, lotions in general and the like, may also be incorporated into the finished products.

Other examples of such materials include but are not limited to odor control agents, such as odor absorbents, activated carbon fibers and particles, baby powder, baking soda, chelating agents, zeolites, perfumes or other odor-masking agents, cyclodextrin compounds, oxidizers, and the like. Superabsorbent particles may also be employed. Additional options include cationic dyes, optical brighteners, humectants, emollients, and the like.

Turning to FIG. 2, once the foamed suspension of fibers is formed in the tank 12 (FIG. 1), the foamed suspension of fibers may be fed to the web forming system 10. As illustrated in FIG. 2, the web forming system 10 may include includes one or more forming zones. In the example embodiment of FIG. 2, three forming zones are shown, including first forming zone 50, second forming zone 52, and third forming zone 54. The forming zones 50, 52, and 54 are positioned along the porous forming surface 26. In one example embodiment, as shown in FIG. 2, the porous forming surface 26 may be at an incline with respect to horizontal. For instance, the porous forming surface 26 may be oriented at an angle with the horizontal of greater than about ten degrees (10°), such as greater than about twenty degrees (20°), such as greater than about thirty degrees (30°), and generally less than about sixty degrees (60°), such as less than about fifty degrees (50°). Each forming zone 50, 52, and 54 may be configured to receive a separate and independent flow of the foamed suspension of fibers for depositing the foamed suspension of fibers onto the forming surface 26. For instance, the first forming zone 50 may deposit a foamed suspension of fibers directly onto the forming surface 26. The second forming zone 52, however, may be configured to deposit a second flow rate of the foamed suspension of fibers on top of the fibers deposited by the first forming zone 50. Similarly, the third forming zone 54 may deposit a flow of the aqueous suspension of fibers on top of the fibers deposited by the first forming zone 50 and the second forming zone 52. In this manner, a multilayered web may be formed. It should be understood, however, that the system and process of the present disclosure may include only a single forming zone for forming single layered webs.

As shown in FIG. 2, each forming zone 50, 52, and 54 may be in fluid communication with a separate and independent foamed fibrous supply line. For instance, first forming zone 50 may be in communication with a first foamed fibrous supply line 56, the second forming zone 52 may be in fluid communication with a second foamed fibrous supply line 58, and the third forming zone 54 may be in fluid communication with a third foamed fibrous supply line 60. The first, second, and third supply lines 56, 58, and 60 may be configured to feed a foamed suspension of fibers to each of the respective forming zones 50, 52, and 54 at a determined and selected flow characteristic, which may be, for instance, flow rate, such as volumetric flow rate, pressure, air content, and/or density. In this regard, each of the supply lines 56, 58, and 60 may be in fluid communication with the mixing tank 12 as shown in FIG. 1 . For instance, the first supply line 56 may include a first injection line 62 that is connected to the mixing tank 12. Similarly, the second supply line 58 may include a second injection line 64, while the third supply line 60 may be in communication with a third injection line 66. The injections lines 62, 64, and 66 may all be in communication with the mixing tank 12 for feeding the foamed suspension of fibers to each of the forming zones 50, 52, and 54. Alternatively, the system 10 may include separate mixing tanks, and each of the first, second, and third injection lines 62, 64, and 66 may be connected to a different, respective mixing tank for feeding the foamed suspension of fibers to the web forming system 10.

As shown, each of the foamed fibrous supply lines 56, 58, and 60 may include a pumping device, a flow meter, such as a volumetric flow meter, a pressure monitoring device, and/or a temperature monitoring device. Each foamed fibrous supply line 56, 58, and 60 may also be in communication with a density monitoring device. The density monitoring device, for instance, may be part of one of the other devices, such as part of the flow meter. Alternatively, the density of the foamed suspension of fibers may be calculated using information received from the other instruments. For example: the first foamed fibrous supply line may include a first pumping device 68, a first flow meter 74, a first pressure monitoring device 80, and a first temperature monitoring device 81 ; the second foamed fibrous supply line 58 may include a second pumping device 70, a second flow meter 76, a second pressure monitoring device 82, and a second temperature monitoring device 83; and the third foamed fibrous supply line 60 may include a third pumping device 72, a third flow meter 78, a third pressure monitoring device 84 and a third temperature monitoring device 85. The pumping devices 68, 70, and 72 may be adjustable such that the foamed suspension of fibers may be independently fed to each forming zone 50, 52, and 54 at a desired, selected flow rate and/or pressure. The flow meters 74, 76, and 78, the pressure monitoring devices 80, 82, and 84 (e.g., volumetric flow rate), and the temperature monitoring devices 81 , 83 and 85 may monitor flow rates, pressures, and temperatures upstream from the forming surface for calculating at least one characteristic of the flow of the foamed suspension of fibers at the forming surface.

In one example embodiment, the flow meters 74, 76, and 78, the pressure monitoring devices 80, 82, and 84, the temperature monitoring devices 81 , 83 and 85 may be placed in communication with one or more controllers. The controllers may include microprocessors or any suitable programmable device. The pumping devices 68, 70, and 72 may also be placed in communication with the one or more controllers. The controllers may be configured to adjust the pumping devices 68, 70, and 72 based upon information received from the flow meters 74, 76, and 78, from the pressure monitoring devices 80, 82, and 84, and/or from the temperature monitoring devices 81 , 83 and 85. In this manner, the foamed suspension of fibers may be fed to each forming zone 50, 52, and 54 at a flow rate within desired set points and/or at a pressure within desired set points for optimizing formation of a web on the forming surface 26.

Information received from the flow meters 74, 76, and 78, from the pressure monitoring devices 80, 82, and 84, and/or from the temperature monitoring devices 81 , 83, and 85 may be used to determine the characteristics of the foamed suspension of fibers at the location of the measurements. In addition, the density of the foamed suspension of fibers may be measured or calculated from the information received from the various instruments. This information, in one embodiment, may be sent to the controllers for then calculating at least one characteristic of the foamed suspension of fibers at the forming surface. In particular, the controller may be programmed to correct the determined volumetric flow rate at the forming surface based upon changes in density, pressure, and temperature. For example, the foamed suspension can experience a pressure drop when being emitted from the supply line onto the forming surface that changes the density of the foamed suspension. One method for calculating downstream values of the foamed suspension, for instance, is disclosed in U.S. Patent No. 4,764,253, which is incorporated herein by reference.

As shown in FIG. 2, opposite the first forming zone 50 along the forming surface 26 may be a first drain device 86 in fluid communication with a first drain line 92. Opposite the second forming zone 52 may be a second drain device 88 in fluid communication with a second drain line 94. Similarly, opposite the third forming zone 54 may be a third drain device 90 in communication with a third drain line 96. The first, second, and third forming zones 50, 52, and 54 may be adjacent to one another along the forming surface 26 and may be positioned on one side of the forming surface 26. The drain devices 86, 88, and 90 may also be adjacent to one another and may be positioned on the opposite side of the forming surface 26 in alignment with the forming zones 50, 52, and 54. As the foamed suspension of fibers is deposited onto the forming surface from each forming zone 50, 52, and 54, a web 14 may be formed and excess fluids may enter the corresponding drain devices 86, 88, and 90. The drain devices may be any suitable static or dynamic drain device capable of draining fluids from the web or from the forming surfaces. The drain device may be a static suction or vacuum box. Alternatively, the drain device may be a drum, such as a rotating drum that applies suction.

As shown in FIG. 2, each drain line 92, 94, and 96 may include a corresponding flow control device, flow meter, temperature monitoring device, and pressure monitoring device. For example: the first drain line 92 may include a first flow control device 98, a first flow meter 104, a first temperature monitoring device 105, and a first pressure monitoring device 110; the second drain line 94 may include a second flow control device 100, a second flow meter 106, a second temperature monitoring device 107, and a second pressure monitoring device 112; and the third drain line 96 may include a third flow control device 102, a third flow meter 108, a third temperature monitoring device 109, and a third pressure monitoring device 114. The flow control devices 98, 100, and 102 may be any suitable device for controlling flow through the line and may be, an adjustable valve or a pump. Pumps, for instance, may be used to apply suction to the forming surface. Alternatively, draining can occur through gravity. In still another example embodiment, each flow control device 98, 100, and 102 may be a combination of a pump and an adjustable valve

In one example embodiment, the system 10 may further include one or more controllers 116. The controllers 116 may include microprocessors or any suitable programmable devices. As shown in FIG. 2, each flow control device 98, 100, and 102, each flow meter 104, 106, and 108, each temperature monitoring device 105, 107, and 109, each density monitoring device, and/or each pressure monitoring device 110, 112, and 114 may be in communication with the controller 116. The controller 116 may receive information from the flow meters 104, 106, and 108, the temperature monitoring devices 105, 107, and 109, the optional density monitoring devices, and/or the pressure monitoring devices 110, 112, and 114 for making adjustments to the flow control devices 98, 100, and 102 for controlling the flow rate in which fluids are drained from each of the drain devices 86, 88, and 90. The combination of receiving information from the flow control devices 98, 100, and 102, which may be volumetric flow meters, from the pressure monitoring devices 110, 112, and 114, from the temperature monitoring devices 105, 107, and 109, and/or from optional density monitoring devices may be used to quantify the fluid discharge flows containing both gases and liquids. In one example embodiment, the controller 116 may use the above information to calculate a flow rate, such as a volumetric flow rate, at the forming surface and control the volumetric flow rate based upon at least one characteristic of the foamed suspension being fed to the forming surface. The controller 116 may then control the flow control devices 98, 100, and 102 to achieve a calculated discharge flow rate through each drain device and drain line.

In example embodiments, the process and system of the present disclosure may further include a sealing zone 120 positioned along the forming fabric 26 and in fluid communication with a sealing fluid supply line 122. As shown in FIG. 2, the sealing fluid supply line 122 may include a pumping device 124, a flow meter 126, a pressure monitoring device 128, and a temperature monitoring device 129. The sealing fluid supply line 122 is for feeding a fluid, particularly a liquid, to the sealing zone 120. Sealing fluid may be any suitable liquid. For instance, the sealing fluid may be water, a water and surfactant solution, or the like. In one example embodiment, the sealing fluid may be non-fibrous. A sealing fluid may be fed to the sealing fluid zone 120 at a flow rate and/or at a pressure such that sealing fluid deposited onto the forming surface 26 forms a fluid seal that prevents air flow in an upstream longitudinal direction. Information received from the flow meter 126, the pressure monitoring device 128, the temperature monitoring device 129, and optionally a density monitoring device may be used to calculate volumetric flow rates of the foam at the forming surface.

As shown in FIG. 2, the sealing zone 120 may be positioned upstream from and adjacent to the plurality of forming zones. The sealing zone 120 may also be placed opposite a sealing drain device 130 connected to a sealing drain line 132. The sealing drain line 132 may include a flow control device 134, a flow meter 136, a temperature monitoring device 137, and a pressure sensing device 138 that may all be in communication with the controller 116. In this manner, the flow rate of drainage of the sealing fluid may be controlled based upon the flow rate or pressure at which the sealing fluid enters or exits the sealing zone 120. By including the sealing zone 120, better formation of the web 14 occurs opposite the first forming zone 50. The web forming system 10 as shown in FIG. 2 may also include a suction zone 140 adjacent to the plurality of formation zones and positioned downstream from the formation zones. The suction zone 140 may be in fluid communication with a drain line 142 which may include a pressure monitoring device 144. The suction zone 140 is for drawing fluids through the embryonic web 14 after the web has been formed. The suction zone 140 is for removing excess fluids, particularly liquids, from the web 14. In one aspect, the drainage flow rate of the foamed suspension of fibers being drained through the one or more drain devices may be controlled such that excess fluid from the one or more forming zones enters the suction zone 140. Ideally, the suction zone 140 facilitates draining fluids from the web 14 without causing any detrimental effects.

As shown in FIG. 2, all of the drain lines 92, 94, 96, 132, and 142 may be fed to a separator tank 150. The separator tank 150 may be configured to separate free gases from foam. As shown, the separator tank 150 may include a gas outlet 152 that may be connected to a vacuum source and a liquid outlet 154. The liquid collected in the separator tank 150 may include a water and surfactant mixture. As shown in FIG. 2, a pumping device 156 may be used to pump liquids from the separator tank 150 to a liquid tank 158 which may also be placed in communication with a water source 160. The liquid tank 158 may be used to recycle the water and surfactant mixture back into the process through the supply lines 56, 58, 60, and 122.

Referring back to FIG. 1 , after the embryonic web 14 is formed from the web forming system or headbox 10, the web 14 may be fed to various different downstream processes. FIG. 1 merely represents one example embodiment of a process for drying the web 14 after being formed. As shown, the web 14 is formed on the forming surface 26 and conveyed downstream. The endless traveling forming fabric 26, for instance, may be supported and driven by rolls 28.

Once formed on the forming fabric 26, the formed web 14 may have a consistency of less than about fifty percent (50%), such as less than about twenty percent (20%), such as less than about ten percent (10%), such as less than about five percent (5%). In fact, the forming consistency may be less than about two percent (2%), such as less than about one and eight-tenths percent (1 .8%), such as less than about one and a half percent (1 .5%). The forming consistency is generally greater than about a half percent (0.5%), such as greater than about eight-tenths percent (0.8%).

Once the wet web 14 is formed on the forming fabric 26, the web 14 is conveyed downstream and optionally further dewatered. For instance, the process may optionally include a plurality of vacuum devices 16, such as vacuum and vacuum rolls. The vacuum boxes assist in removing moisture from the newly formed web 14. As shown in FIG. 1 , the forming fabric 26 may also be placed in communication with a steambox 18 positioned above a pair of vacuum rolls 20. The steambox 18, for instance, may increase dryness and reduce cross-directional moisture variance. The applied steam from the steambox 18 heats the moisture in the wet web 14 causing the water in the web to drain more readily, especially in conjunction with the vacuum rolls 20. From the forming fabric 26, the newly formed web 14 is conveyed downstream and dried. The web 14 may be dried using any suitable drying device. For instance, the web 14 may be through-air dried or placed on a heated drying drum and creped or left uncreped. In FIG. 1 , for instance, the formed web 14 is placed in contact with two heated drying drums 38 and 40. In one example embodiment, from the drying drums 38 and 40, the web 14 may be fed to a through-air dryer prior to being wound into a roll.

The embodiment in FIG. 2 is for forming multilayer webs. In another aspect, the process of the present disclosure may be used to create single layer webs from a foamed suspension of materials.

Turning now to FIG. 3, a system 200 for separating foam from free air and managing foam, e.g . , during foam forming of a nonwoven web, according to an example embodiments of the present disclosure is shown. It will be understood that system 200 may be utilized in or with any foam forming system or process for forming webs from a foamed suspension of fibers. For example, system 200 may be used in or with the example systems and processes shown in FIGS. 1 and 2 and described above. Thus, system 200 is described in greater detail below in the context of the example systems and processes shown in FIGS. 1 and 2. However, it will be understood that system 200 may be used in or with other systems and processes for forming webs from a foamed suspension of fibers in alternative example embodiments.

As shown in FIG. 3, system 200 includes a separator 210 and a tank 230. The separator 210 may be disposed between a headbox, such as web forming system 10 (FIG. 1), and the tank 230. Moreover, separator 210 may be disposed along a flow path for foam between the headbox and the tank 230. Thus, separator 210 may receive foam flowing from the headbox to the tank 230. Separator 210 may be configured to separate free gases from the foam in separator 210. The headbox and the separator 210 may be connected via pluming, piping, conduits, etc.

Separator 210 may include an inlet 220, a first outlet 222, and a second outlet 224. Inlet 220 may be in fluid communication with the headbox, and a flow of foam FF may enter separator 210 through inlet 220. As shown, separator 210 may include a plurality of inlets 220 in example embodiments. Each of the inlets 220 may be connected and in fluid communication with a respective one of drain lines 92, 94, 96, 132, and 142 (FIG. 2). Thus, foam from various portions of web forming system 10 may enter separator 210 via a respective one of inlets 220. In other example embodiments, two or more streams of foam from web forming system 10 may be combined upstream of separator 210 and enter separator 210 via a single inlet.

First outlet 222 may be in fluid communication with the tank 230, and the flow of foam FF may exit separator 210 through first outlet 222. Thus, the flow of foam FF may pass through first outlet 222 on the flow path for foam between the headbox and the tank 230. Second outlet 224 may be in fluid communication with a vacuum source 270, and a flow of free air FA may exit separator 210 through second outlet 224. Moreover, vacuum source 270 may be operable to generate a vacuum within an interior volume 216 of separator 210. The vacuum within the interior volume 216 of separator 210 may draw and remove large air bubbles from within the foam in separator 210. The free air from the large air bubbles may then exit separator 210 through second outlet 224. In contrast, air entrained within the foam as dispersed gas bubbles may remain within the flow of foam FF and exit separator 210 through first outlet 222.

As noted above, separator 210 may be configured for removing free air from the flow of foam FF passing though separator 210 between the headbox and the tank 230. Gravity may facilitate separation of the free air from the foam within separator 210. Moreover, the relatively denser foam may settle towards the bottom portion 212 of the separator 210, and the relatively less dense free air may rise towards the top portion 214 of the separator 210 assisted by the vacuum within the interior volume 216 of separator 210 To assist with separation of the free air from the flow of foam FF, the first and second outlets 222, 224 may be spaced apart on separator 210. For example, separator 210 may extend between a bottom portion 212 and a top portion 214, e.g., along a vertical direction V. The first outlet 222 may be positioned at the bottom portion 212 of the separator 210, and the second outlet 224 may be positioned at the top portion 214 of the separator 210. Thus, e.g., the first and second outlets 222, 224 may be spaced apart along the vertical direction V on the separator 210 and/or positioned opposite each other along the vertical direction V on the separator 210. Moreover, the first outlet 222 may be positioned to receive the relatively denser foam that settles towards the bottom portion 212 of the separator 210, and the second outlet 224 may be positioned to receive the relatively less dense free air that rises towards the top portion 214 of the separator 210. The inlet(s) 220 may be positioned between the first and second outlets 222, 224, e.g., along the vertical direction V. Thus, the flow of foam FF may enter the interior volume 216 of separator 210 between the first and second outlets 222, 224 and/or at a middle portion of the separator 210.

Tank 230 may be in fluid communication with separator 210. Moreover, the flow of foam FF may exit separator 210 through first outlet 222 and flow to the tank 230. The separator 210 and tank 230 may be connected via pluming, piping, conduits, etc. Within the tank 230, water, surfactant(s), or other fluids may be added to the foam in tank 230. T ank 230 may also be in fluid communication with the headbox, e.g., web forming system 10 (FIG. 2), such that the foam in tank 230 may be reintroduced into the headbox for foam forming of a nonwoven web at the headbox. Thus, the tank 230 may be configured for recycling of the flow of foam FF back into the foam forming process. The tank 230 and the headbox may be connected via pluming, piping, conduits, etc. In certain example embodiments, an interior volume 232 of the tank 230 may be contiguous with ambient atmosphere. Thus, e.g., the pressure within the interior volume 232 of the tank 230 may be greater than the vacuum within the interior volume 216 of separator 210 during operation of system 200. In example embodiments, the interior volume 232 of the tank 230 may be contiguous with ambient atmosphere via a valve 234. In other example embodiments, the top portion of tank 230 may include an opening or other connection to ambient atmosphere. The interior volume 232 of the tank 230 may be greater than the interior volume 216 of separator 210. For example, the interior volume 232 of the tank 230 may be no less than two times (2X) greater, no less than five times (5X) greater, no less than ten times (10X) greater than the interior volume 216 of separator 210.

System 200 also includes features for maintaining a level of the foam LF in the separator 210. As shown in FIG. 3, system 200 includes a pump 240 and a sensor 250. Pump 240 may be disposed along the flow path for foam between the headbox and the tank 230. For example, pump 240 may be disposed downstream of the first outlet 222, e.g., between the separator 210 and the tank 230. Pump 240 may be operable to flow the foam out of the interior volume 216 of separator 210 via first outlet 222. Moreover, the flow of foam FF may exit separator 210 at first outlet 222 during operation of the pump 240. In certain example embodiments, the pump 240 may be a positive displacement pump, such as a rotary, reciprocating, or linear positive displacement pump. Utilizing a positive displacement pump may advantageously assist with pumping the foam from separator 210 via first outlet 222 during the operation of the pump 240, e.g., due to the ability of positive displacement pumps to handle viscous fluids more efficiently than centrifugal pumps. Because the foam in the flow of foam FF can be non-Newtonian, the density and viscosity of the foam in the flow of foam FF can change based upon the location and the process. Thus, the pump 240 may be particularly suitable for pumping foam when the pump 240 is a positive displacement pump. However, it will be understood that pump 240 may be a centrifugal pump in alternative example embodiments.

The sensor 250 may be operable to determine the level of the foam LF in the separator 210. For example, sensor 250 may detect and/or measure a height of the level of the foam LF within the interior volume 216 of separator 210, e.g., along the vertical direction V. The level of the foam LF may correspond to a boundary between the foam and the free air within the interior volume 216 of separator 210. For example, as noted above, separator 210 may separate the free air from the foam within separator 210. The free surface of the foam that faces the top portion 214 of the separator 210 may correspond to the level of the foam LF in the separator 210. The sensor 250 may be configured to detect the level of the foam LF. As an example, sensor 250 may be a capacitive rod mounted to the separator 210 and extending into the interior volume 216 of separator 210. For instance, the capacitive rod may be mounted to separator 210 at the top portion 214 of the separator 210 and may extend downwardly along the vertical direction V towards the bottom portion 212 of the separator 210. The capacitive rod may detect a change in capacitance that varies as a function of the level of the foam LF in the separator 210 and may output a signal that corresponds to the level of the foam LF in the separator 210. Other sensors may also be used to detect the level of the foam LF in the separator 210. For example, the sensor 250 may include an optical sensor, camera, ultrasonic sensor, a radar sensor, etc. configured to sense the level of the foam LF in the separator 210 and output a signal that corresponds to the level of the foam LF in the separator 210.

System 200 may also include or be in operative communication with a processing device or a controller 260 that may be generally configured to facilitate operation of at least a portion of system 200. In this regard, pump 240, sensor 250, and other components of system 200 may be in communication with controller 260. Thus, e.g., the controller 260 may receive inputs from the sensor 250 and may adjust operation of pump 260 based at least in part on the inputs from the sensor 250. Pump 240, sensor 250, and other components of system 200 may be in communication with controller 260 via, for example, one or more signal lines or shared communication busses. In this manner, Input/Output (“I/O”) signals may be routed between controller 260 and various operational components of system 200.

As used herein, the terms “processing device,” “computing device,” “controller,” or the like may generally refer to any suitable processing device, such as a general or special purpose microprocessor, a microcontroller, an integrated circuit, an application specific integrated circuit (ASIC), a digital signal processor (DSP), a field-programmable gate array (FPGA), a logic device, one or more central processing units (CPUs), a graphics processing units (GPUs), processing units performing other specialized calculations, semiconductor devices, etc. In addition, these “controllers” are not necessarily restricted to a single element but may include any suitable number, type, and configuration of processing devices integrated in any suitable manner to facilitate appliance operation. Alternatively, controller 260 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND/OR gates, and the like) to perform control functionality instead of relying upon software.

Controller 260 may include, or be associated with, one or more memory elements or non- transitory computer-readable storage mediums, such as RAM, ROM, EEPROM, EPROM, flash memory devices, magnetic disks, or other suitable memory devices (including combinations thereof). These memory devices may be a separate component from the processor or may be included onboard within the processor. In addition, these memory devices may store information and/or data accessible by the one or more processors, including instructions that may be executed by the one or more processors. It should be appreciated that the instructions may be software written in any suitable programming language or may be implemented in hardware. Additionally, or alternatively, the instructions may be executed logically and/or virtually using separate threads on one or more processors.

For example, controller 260 may be operable to execute programming instructions or microcontrol code associated with an operating cycle of system 200. In this regard, the instructions may be software or any set of instructions that when executed by the processing device, cause the processing device to perform operations, such as running one or more software applications, adjusting the operating parameters of pump 240, etc. Moreover, it should be noted that controller 260 as disclosed herein is capable of and may be operable to perform any methods, method steps, or portions of methods as disclosed herein. For example, in some example embodiments, methods disclosed herein may be embodied in programming instructions stored in the memory and executed by controller 260.

The memory devices may also store data that may be retrieved, manipulated, created, or stored by the one or more processors or portions of controller 260. The data may include, for instance, data to facilitate performance of methods described herein. The data may be stored locally (e.g., on controller 260) in one or more databases and/or may be split up so that the data is stored in multiple locations. In addition, or alternatively, the one or more database(s) may be connected to controller 260 through any suitable network(s), such as through a high bandwidth local area network (LAN) or wide area network (WAN). In this regard, for example, controller 260 may further include a communication module or interface that may be used to communicate with one or more other component(s) of system 200, controller 260, or any other suitable device, e.g., via any suitable communication lines or network(s) and using any suitable communication protocol. The communication interface may include any suitable components for interfacing with one or more network(s), including for example, transmitters, receivers, ports, controllers, antennas, or other suitable components. The controller 260 may be configured for controlling operation of the pump 240 in order to maintain the level of foam LF within the separator 210. For example, the controller 260 may receive a signal from the sensor 250 corresponding to the level of the foam LF in the separator 210. Based at least in part on the level of the foam LF in the separator 210, the controller 260 may operate the pump 240 to maintain the level of the foam LF within a determined range within the separator 210. As an example, the controller 260 may adjust the operation of pump 240 to increase the flow rate of the flow of foam FF from the separator 210 in response to the detected level of the foam LF from sensor 250 being greater than the determined range R. Conversely, the controller 260 may adjust the operation of pump 240 to decrease the flow rate of the flow of foam FF from the separator 210 in response to the detected level of the foam LF from sensor 250 being less than the determined range R. The determined range R may be selected to limit or prevent over-draining and/or under-draining of foam from the separator 210. For instance, a lower value of the determined range R may be positioned above the first outlet 222 along the vertical direction V, and an upper value of the determined range R may be positioned below the second outlet 224 along the vertical direction V. As a specific example, the lower value of the determined range R may be positioned no less than twenty-five centimeters (25 cm) above the first outlet 222 along the vertical direction V, and the upper value of the determined range R may be positioned no less than twenty-five centimeters (25 cm) below the second outlet 224 along the vertical direction V. Such spacing may advantageously assist with limiting or preventing over-draining and/or under-draining of foam from the separator 210. In example embodiments, the determined range R may be less than fifty centimeters (50 cm), less than twenty-five centimeters (25 cm), less than ten centimeters (10 cm), etc. along the vertical direction V. Such sizing of the determined range R may assist with providing a consistent residence time for foam in the separator 210 during operation of system 200.

A shown in FIG. 3, system 200 may also include an additional pump 280. The additional pump 280 may be disposed downstream of the tank 230. The additional pump 280 may be operable to flow foam from the tank 230 to the headbox, e.g., web forming system 10 (FIG. 2). In example embodiments, the additional pump 280 may include a fan pump. By maintaining the level of foam LF within the determined range R, the additional pump 280 may operate with increased efficiency and robustness. Moreover, in example embodiments, the additional pump 280 may not utilize vacuum assistance due to the pump 240 maintaining the level of foam LF within the determined range R.

FIG. 4 illustrates a method 400 for foam forming according to an example embodiment of the present subject matter. As an example, method 400 may be used in or with system 200 (FIG. 3) to assist with maintaining a level of foam within a vacuum separator. The controller 260 of system 200 may be programmed or configured to implement method 400. While method 400 is described in greater detail below in the context of system 200, it will be understood that method 400 may be used in or within any suitable system or process in alternative example embodiments.

At 410, foam may be flowed from a headbox, such as the web forming system 10 (FIG. 2), to a vacuum separator, such as the separator 210 (FIG. 3). Thus, the flow of foam FF may enter separator 210 at 410. At 420, free air from the foam may flow out of the vacuum separator, e.g., via the second outlet 224.

At 430, a level of foam in the vacuum separator may be determined. For example, sensor 250 may detect and/or measure the level of the foam LF within the interior volume 216 of separator 210 at 430, and the sensor 250 may output a signal corresponding to the level of the foam LF. At 440, the level of the foam LF may be compared to a determined range. For example, the controller 260 may compare the determined level of the foam LF from the sensor 250 to the determined range.

Method 400 may also include controller operation of a pump based on the comparison of the level of the foam to the determined range. For example, at 450, an operating parameter of the pump may be adjusted to change a flow rate of foam from the vacuum separator when the detected level of the foam is outside of the determined range. In certain example embodiments, at 450, the controller 260 may increase the operating speed of the pump 240 in order to increase the flow rate of the flow of foam FF from the separator 210 when the detected level of the foam LF from sensor 250 is greater than the determined range R. Conversely, in such example embodiments, the controller 260 may decrease the operating speed of the pump 240 at 450 in order to decrease the flow rate of the flow of foam FF from the separator 210 when the detected level of the foam LF from sensor 250 is less than the determined range R. At 460, the operating parameter of the pump may be maintained or held constant to maintain the flow rate of foam from the vacuum separator when the detected level of the foam is within the determined range. In certain example embodiments, at 460, the controller 260 may maintain the operating speed of the pump 240 in order to keep the flow rate of the flow of foam FF from the separator 210 constant when the detected level of the foam LF from sensor 250 is within the determined range R.

In example embodiments, an average residence time of the foam in the vacuum separator may substantially constant during method 400. Thus, e.g., the average residence time of foam in the separator 210 may vary by less than one minute (1 min), less than thirty seconds (30 s), less than ten seconds (10 s), etc. during method 400. Such consistent residence time may advantageously improve stability of foam during method 400. During method 400, an interior of the vacuum separator may be under vacuum. Thus, e.g., vacuum source 270 may operate during method 400 in order to generate a vacuum within the interior volume 216 of separator 210 and thereby draw and remove large air bubbles from within the foam in separator 210. During method 400, an interior volume of a backwater tank that receives the flow of foam from the vacuum separator may be contiguous with ambient atmosphere. Thus, e.g., the interior volume 232 of the tank 230 may be contiguous with ambient atmosphere during method 400 as the flow of foam FF exits separator 210 and flows to tank 230.

FIG. 4 depicts steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that the steps of any of the methods discussed herein may be adapted, rearranged, expanded, omitted, or modified in various ways without deviating from the scope of the present disclosure.

These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.

EXAMPLE EMBODIMENTS

First example embodiment: A foam forming system, comprising: a headbox; a tank; a separator disposed between the headbox and the tank along a flow path for foam between the headbox and the tank, the separator comprising an inlet for the foam, a first outlet for the foam, and a second outlet for free air from the foam; a pump; a sensor operable to determine a level of the foam in the separator; and a controller configured to receive a signal from the sensor corresponding to the level of the foam in the separator, and, based at least in part on the level of the foam in the separator, operate the pump to maintain the level of the foam within a determined range within the separator.

Second example embodiment: The foam forming system of the first example embodiment, further comprising an additional pump disposed downstream of the tank in a flow path for foam between the tank and the headbox, the additional pump operable to flow the foam along the flow path between the headbox and the tank.

Third example embodiment: The foam forming system of the second example embodiment, wherein the additional pump comprises a fan pump.

Fourth example embodiment: The foam forming system of any one of first through third example embodiments, wherein inlet is disposed between the first and second outlets along a vertical direction.

Fifth example embodiment: The foam forming system of any one of the first through the fourth example embodiments, wherein the first outlet is positioned at a bottom portion of the separator, and the second outlet is positioned at a top portion of the separator.

Sixth example embodiment: The foam forming system of any one of first through the fifth example embodiments, further comprising a vacuum source coupled to the separator via the second outlet of the separator, the vacuum source operable to generate a vacuum within an interior volume of the separator.

Seventh example embodiment: The foam forming system of the sixth example embodiment, wherein an interior volume of the tank is contiguous with ambient atmosphere.

Eighth example embodiment: The foam forming system of any one of the first through seventh example embodiments, wherein the pump comprises a positive displacement pump.

Nineth example embodiment: The foam forming system of any one of the first through eighth example embodiments, wherein the sensor comprises a capacitive rod.

Tenth example embodiment: The foam forming system of any one of the first through nineth example embodiments, wherein a volume of the tank is greater than a volume of the separator. Eleventh example embodiment: A foam forming system, comprising: a tank; a vacuum separator comprising an inlet for foam, a first outlet for the foam, and a second outlet for free air from the foam, the vacuum separator coupled to the tank via the first outlet such that the foam is flowable from the vacuum separator to the tank; a pump operable to flow the foam from the vacuum separator to the tank; a sensor operable to determine a level of the foam in the vacuum separator; and a controller configured to determine the level of the foam in the vacuum separator based at least in part on a signal from the sensor, and operate the pump to maintain the level of the foam within a determined range within the vacuum separator based at least in part on the determined level of the foam in the vacuum separator.

Twelfth example embodiment: The foam forming system of the eleventh example embodiment, further comprising an additional pump disposed downstream of the tank, the additional pump operable to flow the foam from the tank.

Thirteenth example embodiment: The foam forming system of either the eleventh or the twelfth example embodiments, wherein inlet is disposed between the first and second outlets along a vertical direction.

Fourteenth example embodiment: The foam forming system of any one of the eleventh though thirteenth example embodiments, wherein the first outlet is positioned at a bottom portion of the vacuum separator, and the second outlet is positioned at a top portion of the vacuum separator.

Fifteenth example embodiment: The foam forming system of any one of the eleventh through fourteenth example embodiments, further comprising a vacuum source coupled to the vacuum separator via the second outlet of the vacuum separator, the vacuum source operable to generate a vacuum within an interior volume of the vacuum separator.

Sixteenth example embodiment: The foam forming system of the fifteenth example embodiment, wherein an interior volume of the tank is contiguous with ambient atmosphere.

Seventeenth example embodiment: A method for foam forming, comprising: flowing foam from a headbox to a vacuum separator; flowing free air from the foam out of the vacuum separator through a vacuum outlet of the vacuum separator; and operating a pump to flow the foam out of the vacuum separator through a foam outlet of the vacuum separator, wherein operating the pump comprises determining a level of the foam in the vacuum separator with a sensor and adjusting a flow rate of the pump to maintain the level of the foam within a determined range within the vacuum separator based at least in part on the determined level of the foam in the vacuum separator.

Eighteenth example embodiment: The method of the seventeenth example embodiment, wherein an interior of the vacuum separator is under vacuum. Nineteenth example embodiment: The method of either the seventeenth example embodiment or the eighteenth example embodiment, wherein a residence time of the foam in the vacuum separator is substantially constant.

Claims

What Is Claimed:

1 . A foam forming system, comprising: a headbox; a tank; a separator disposed between the headbox and the tank along a flow path for foam between the headbox and the tank, the separator comprising an inlet for the foam, a first outlet for the foam, and a second outlet for free air from the foam; a pump; a sensor operable to determine a level of the foam in the separator; and a controller configured to receive a signal from the sensor corresponding to the level of the foam in the separator, and based at least in part on the level of the foam in the separator, operate the pump to maintain the level of the foam within a determined range within the separator.

2. The foam forming system of claim 1 , further comprising an additional pump disposed downstream of the tank in a flow path for foam between the tank and the headbox, the additional pump operable to flow the foam along the flow path between the headbox and the tank.

3. The foam forming system of claim 2, wherein the additional pump comprises a fan pump.

4. The foam forming system of any one of claims 1 through 3, wherein inlet is disposed between the first and second outlets along a vertical direction.

5. The foam forming system of any one of claims 1 through 4, wherein the first outlet is positioned at a bottom portion of the separator, and the second outlet is positioned at a top portion of the separator.

6. The foam forming system of any one of claims 1 through 5, further comprising a vacuum source coupled to the separator via the second outlet of the separator, the vacuum source operable to generate a vacuum within an interior volume of the separator.

7. The foam forming system of claim 6, wherein an interior volume of the tank is contiguous with ambient atmosphere.

8. The foam forming system of any one of claims 1 through 7, wherein the pump comprises a positive displacement pump.

9. The foam forming system of any one of claims 1 through 8, wherein the sensor comprises a capacitive rod.

10. The foam forming system of any one of claims 1 through 9, wherein a volume of the tank is greater than a volume of the separator.

11. A foam forming system, comprising: a tank; a vacuum separator comprising an inlet for foam, a first outlet for the foam, and a second outlet for free air from the foam, the vacuum separator coupled to the tank via the first outlet such that the foam is flowable from the vacuum separator to the tank; a pump operable to flow the foam from the vacuum separator to the tank; a sensor operable to determine a level of the foam in the vacuum separator; and a controller configured to determine the level of the foam in the vacuum separator based at least in part on a signal from the sensor, and operate the pump to maintain the level of the foam within a determined range within the vacuum separator based at least in part on the determined level of the foam in the vacuum separator.

12. The foam forming system of claim 11 , further comprising an additional pump disposed downstream of the tank, the additional pump operable to flow the foam from the tank.

13. The foam forming system of either claim 11 or claim 12, wherein inlet is disposed between the first and second outlets along a vertical direction.

14. The foam forming system of any one of claims 11 through 13, wherein the first outlet is positioned at a bottom portion of the vacuum separator, and the second outlet is positioned at a top portion of the vacuum separator.

15. The foam forming system of any one of claims 11 through 14, further comprising a vacuum source coupled to the vacuum separator via the second outlet of the vacuum separator, the vacuum source operable to generate a vacuum within an interior volume of the vacuum separator.

16. The foam forming system of claim 15, wherein an interior volume of the tank is contiguous with ambient atmosphere.

17. A method for foam forming, comprising: flowing foam from a headbox to a vacuum separator; flowing free air from the foam out of the vacuum separator through a vacuum outlet of the vacuum separator; and operating a pump to flow the foam out of the vacuum separator through a foam outlet of the vacuum separator, wherein operating the pump comprises determining a level of the foam in the vacuum separator with a sensor and adjusting a flow rate of the pump to maintain the level of the foam within a determined range within the vacuum separator based at least in part on the determined level of the foam in the vacuum separator.

18. The method of claim 17, wherein an interior of the vacuum separator is under vacuum.

19. The method of either claim 17 or claim 18, wherein a residence time of the foam in the vacuum separator is substantially constant.