System and Method for Foam Fractionation

Embodiments of the disclosure provide a foam fractionation method and system that include a foam collection container having a body, a collection tube coupled to the collection container, and a foam collection conduit coupled with foam removal piping disposed within a chamber formed by the body of the collection cone. The collection container and the collection tube are coupled to allow for pressurization within the chamber. A mouth of the foam collection conduit is operable to receive foam.

BACKGROUND

Unfiltered fine particles in recirculating aquaculture systems can promote the development of bacterial cultures that consume oxygen and generate unwanted carbon dioxide and/or ammonia. Such particles can also irritate fish gills, which can make fish within the aquaculture system more susceptible to disease. Foam fractionators or protein skimmers can be used as an effective treatment for the removal of fine particles, which include organic compounds such as food and waste, in aquaculture systems. Fractionators or skimmers can also be used to harvest algae and/or phytoplankton gently enough to maintain viability for culturing or commercial sale as live cultures. Systems employing foam fractionation are commonly used in commercial applications such as municipal water treatment facilities, large scale aquaculture facilities, and public aquariums. When used in recirculating aquaculture systems, foam fractionators are typically stand-alone treatment vessels that are operated in a side-stream pumping system. Due to the difficulty of sealing foam fractionation devices, most recirculating aquaculture systems only treat a portion of the total flow with foam fractionation.

Foam fractionation systems generally operate to remove organic compounds, which may include proteins and/or amino acids, by leveraging the polarity of the organic compound itself. Due to an inherent electrical charge of organic compounds, water-borne proteins are either repelled or attracted by the air and water interface when bubbles are formed. Such molecules are typically either hydrophobic, such as fats and oils, or hydrophilic, such as salt, sugar, ammonia, most amino acids, and most inorganic compounds. However, some larger organic molecules can have both hydrophobic and hydrophilic portions and are referred to as being amphipathic or amphiphilic. Some commercial protein skimmers work by generating a large air/water interface by injecting large numbers of bubbles into a water column, thus, creating the bubble surfaces upon which molecules can attach. In general, achieving smaller bubbles results in a more effective protein skimming process because the outer surface area of small bubbles occupying a volume is greater than the outer surface area of large bubbles occupying the same volume.

Thus, large numbers of small bubbles can present an enormous air and water interface where hydrophobic organic molecules and amphipathic organic molecules collect or adsorb at the surface of the air bubbles. Also, fluid movement hastens the diffusion of organic molecules from the water because more organic molecules are effectively adsorbed when promulgating more contact between these particles and the surface of the air bubbles. This process continues until the interface is saturated with air bubbles, which can create foam, unless the bubbles are removed from the water or they burst, in which case the accumulated molecules are released back into the water, though now transported closer to the surface where they can be picked up by other bubbles.

As the bubbles migrate toward the water surface due to a buoyant force, the bubbles form a dense cluster, thereby creating a foam that carries the organic molecules attached to the outer bubble surfaces to a skimmate collection device or a waste collector. Thereafter, the organic molecules, and any inorganic molecules that have become bound to the organic molecules, can be exported from the water system. Existing foam fractionation systems are generally capable of removing foam from small-scale systems, or portions of large scale systems, however, a need exists to allow for a modular, controllable, and scalable foam fractionation system that allows for treatment of the full flow of water in large-scale aquaculture systems.

Therefore, it is desirable to develop a foam fractionation device that provides for the removal of foam having undesirable molecules trapped in foam via a controllable, efficient, and modular system.

SUMMARY

Some embodiments provide a foam fractionation device that includes a foam collection container having a body, a collection tube coupled to the collection container, and a foam collection conduit coupled with foam removal piping disposed within a chamber formed by the body of the foam collection container. The foam collection container and the collection tube are coupled to allow for pressurization within the chamber. A mount of the foam collection conduit is operable to receive foam.

Other embodiments include a foam fractionation system comprising a channel having a first portion and a second portion, a sump disposed within the channel intermediate the first portion and the second portion, an air injection system disposed along a bottom surface of the sump, and a foam fractionation device disposed within the sump above the air injection system. The device includes a foam collection cone forming a chamber, a collection tube coupled with the collection cone, and a foam collection conduit coupled with foam removal piping disposed within the body of the foam collection cone. In some embodiments, the system includes a first wall disposed between the sump and the second portion of the channel.

Further embodiments include a method of fractionation that includes flowing water through a channel having a first portion and a second portion, injecting air through an air injection system disposed within a sump, the sump located intermediate the first portion and the second portion of the channel, receiving foam into a foam fractionation device, the foam fractionation device disposed within the sump above the air injection system, the device comprising a foam collection container defining a chamber, a collection tube coupled with the foam collection cone, and a foam collection conduit coupled with foam removal piping disposed within the chamber defined by the foam collection conduit, and pressurizing the foam removal piping with a pressure regulating device to regulate an internal water level within the chamber.

DETAILED DESCRIPTION

FIGS. 1-3illustrate embodiments of fractionation devices22of different full flow fractionation systems20that includes a plurality of fractionation devices22, which are generally modular and scalable. In some embodiments, only a single fractionation device22may be utilized, but in other embodiments, any suitable number of fractionation devices22may be utilized. Referring toFIG. 1, a plurality of the fractionation devices22are disposed in-line within a flow channel24. The plurality of devices22may be installed orthogonal to the direction of flow of water, as shown inFIG. 1, within a first portion26of the flow channel24. As will be described in greater detail below, water flows through the first portion26of the flow channel24into a sump30, where bubbles are formed by an air release system32at a lower end of the sump30. The bubbles move upward in the water flowing through the sump30due to a buoyant force in the direction of arrows36. The bubbles carry particles disposed along an outer surface of the bubbles to the surface of the water, where the bubbles form a foam that is removed from the water through the one or more modular fractionation device22, as discussed in more detail below. After passing by the air release system32within the sump30, the water moves through a plurality of apertures38or other conduits within a first wall40to a second portion42of the flow channel24.

Still referring toFIG. 1, the first portion26of the flow channel24is partially defined by a first bottom surface50. The sump30is partially defined by the first wall40, a second wall52parallel to the first wall40and which extends from the first bottom surface50, a second bottom surface54within which the air release system32is positioned, a third wall56disposed orthogonally to and between the first and second walls40,52, and a fourth wall (not shown) parallel with the third wall56such that the fourth wall encloses the sump30. In some embodiments, fewer or more than four walls may be included. In some embodiments, a cylindrical first wall40may be used. Disposed along the second bottom surface54is the air release system32, which includes a plurality of air injectors60. While the term air injector60is used herein, air injection can occur by any suitable method or device, for example, one or more of a venture, an aerator such as a Toring Turbine®, bubble diffuser, any other suitable devices that create small bubbles, or combinations thereof. In some embodiments, the air release system32is located along a different surface defining the flow channel24. In some embodiments, the first wall40includes the plurality of apertures38disposed along a lower end62thereof. In some embodiments, the plurality of apertures38are disposed along a medial portion64of the first wall40. The plurality of apertures38allow for flow of water between the sump30and the second portion42of the flow channel24.

The air injectors60of the air release system32are operable to release air into the water within the sump30. The one or more air injectors60may be formed in rows and/or columns along the second bottom surface54within the sump30. The one or more air injectors60release air into the water within the sump30, thereby forming bubbles. It is contemplated that any size bubble may be formed by the one or more air injectors60, however, smaller bubbles may be used because small bubbles can be more effective at capturing more organic matter as the bubbles rise to a surface of the water. Further, the rate of air release may be adjusted, or adjustable by a controller or a human operator. In some embodiments, the rate of injection of the bubbles may be adjusted based on feedback received from one or more sensors within the system20, as described in greater detail hereinafter below. The foam fractionation device22and system20are contemplated for application in freshwater, water of some amount of salinity, or any other composition of water containing particulates and having a surface tension capable of supporting the production of bubbles by the air release system32.

Referring now toFIG. 2, a cross sectional view of one of the plurality of foam fractionation devices22of a further embodiment of full flow fractionation system20is shown. Each device22includes a foam collection container or cone70that may include a body72and a neck74that extends from an upper end76of the body72. An opening78is provided at a lower end80of the body, the opening78being sized to receive bubbles rising in the water within the body and/or water depending on a pressure level within foam removal piping82, as will be discussed in greater detail hereinafter below. Adjacent the neck74is a collection pipe84. The collection pipe84may be fittingly received by an inner surface86of the neck74, or may be connected to the neck74with a clamp, an adhesive, or any other suitable connector. In some embodiments, the collection pipe84may be fittingly received along an outer surface88of the neck74. The neck74of the cone70and the collection pipe84may be connected via a friction fit, an interference fit, a press fit, one or more clamps, soldering or any other suitable form of coupling. Further, any of the conduit or piping described herein may be connected to another pipe with an interference fit, a press fit, one or more clamps, soldering, or any other suitable form of coupling. The collection pipe84may be removable to allow for cleaning of one or more components of the device22. Although the foam collection container or cone70is shown herein as being an inverted cone, the foam collection container or cone70may have any other suitable shape.

Still referring toFIG. 2, a removable cap100and a spray tip102may be positioned at an upper end of the collection pipe84. In other embodiments, the collection pipe84may not be necessary and, for example, the cap100and/or spray tip102may be attached to a top portion of the cone70in any suitable manner. During use of the system20, the collection pipe84, the removable cap100, and the spray tip102are connected in such a fashion that allows for pressurization within the body72of the cone70. However, in some embodiments, one or more of the collection pipe84, the removable cap100, and the spray tip102are removable for cleaning purposes, or for some other reason.

A foam collection funnel104is positioned within the cone70and generally concentric with the collection pipe84. While the flannel104is shown as being frustoconical, in alternative embodiments the funnel104may be in the form of a conduit having any other suitable shape. In illustrative embodiments, the foam collection funnel104is inverted with respect to the cone70, i.e., a widest portion of the funnel104is at an upper end thereof, while the widest portion of the cone70is at a lower end thereof. The relative vertical positions of the cone and the funnel104may be varied, for example, the funnel104may be positioned lower than as shown inFIG. 2(i.e., midway along a height of the cone70). A head space106exists between a mouth108of the foam collection funnel104and the removable cap100. The mouth108of the foam collection funnel104is generally positioned within the collection pipe84, and a funnel neck110is in fluid communication with a foam removal pipe112.

In other illustrative embodiments, for example, in embodiments without the collection pipe84, the mouth108of the foam collection funnel104may be positioned within the cone70. The loam removal pipe112is a component of the piping82. The foam removal pipe112extends downward, through the opening78of the cone70to a removal conduit114. The removal conduit114is also a component of the piping82. The removal pipe112and the removal conduit114may be made of the same material or may be different materials, but are generally fluidly coupled to allow for the discharge of foam through the foam collection funnel104and out to a waste disposal. The removal pipe112may be connected to removal conduit114in such a means as to allow the removal conduit114to articulate in a linear grade promoting the gravitationally induced flow of foam through the removal conduit114while permitting the substantially vertical articulation of removal pipe112. The means of connection may include a coupling of flexible material, rigid material of a suitable shape to promote the angled removal conduit114, welding or fusion, adhesive, fastening, or any other suitable means of joining the removal pipe112to removal conduit114for facilitating the flow of foam.

Still referring toFIG. 2, the fractionation device22is connected to a first or lower beam120with one or more connectors122. The connectors122may be generally cylindrical members that intersect bores along the cone70and connect the first beam120with an upper or second beam124(as shown inFIG. 3). In some embodiments, the connectors122are coupled with a clamp126at a lower end thereof, and are coupled with a strip128at an upper end thereof. In some embodiments, four connectors122are included to connect the cone70with one of the lower beams120and one of the upper beams124. In some embodiments, one or more different connectors may be utilized. The connectors122help to hold the device22in place stabilize the device22) during use thereof. The foam collection cone70may have one or more bores130through which one or more of the connectors122are secured.

As illustrated inFIG. 2, one or more baffles140are disposed below the foam collection cone70of the fractionation device22. The one or more baffles140may include a slanted surface142disposed within the water, beneath an operational water level144. The slanted surfaces142of the one or more baffles140operate to route bubbles formed within the sump30to a middle of the one or more fractionation devices22. The bubbles move upward in the direction of the arrows36toward the opening78of the foam collection cone70. The bubbles rise up to an internal water level150, which may be lower than the operational water level144due to back pressure within the piping82. As the bubbles hit the internal water level150, foam is generated and, as foam accumulates, the foam travels up into the cone70above the internal water level150. As the foam reaches the foam collection funnel104, the flow velocity may increase due to the reduced area between the foam collection funnel104and the foam collection cone70.

The foam is then forced above the mouth108, down into the funnel104, and drains to the removal piping82. The back pressure within the removal piping82may be controlled with a pressure regulator (not shown), as discussed in greater detail hereinafter below, or by any other suitable method for regulating pressure, such as a partially closed valve. In some embodiments, the internal water level150may be adjusted by modifying a back pressure in the cone70. A chamber152is formed between the internal water level150, an internal surface154of the cone70, the collection pipe84, and the cap100(if utilized). While the internal water level150is disclosed herein as being adjustable, the operational water level144may also be adjusted.

While a particular method for supporting the cone70is disclosed herein, one skilled in the art will understand that the cone70and/or other components of the systems disclosed herein may be supported in any suitable manner.

The foam collection cone70may be made of one or more of a number of materials including, but not limited to, polyethylene terephthalate (PET), polyethylene (PE), high-density polyethylene (HDPE), polyvinyl chloride (PVC), low-density polyethylene (LDPE), polypropylene (PP), Polystyrene (PS), polycarbonate (PC), or another polymer. In some embodiments, the collection cone70may comprise a metal or glass. Further, the components that comprise the device22, i.e., the connectors122, the funnel104, the piping82, the collection pipe84, the spray tip102, or the cap100, may be made of one of the aforementioned materials, or any other suitable material or combination of materials.

Referring now toFIG. 3, two devices22are shown in cross section. As shown in the figure, the one or more connectors122may be coupled with an outer surface160of the cone70by one or more brackets162that may be screwed, riveted, adhesively coupled, or coupled in some other fashion thereto. The foam collection cone70may be attached, via the connectors122to the one or more lower and/or upper beams120,124. The one or more lower and upper beams120,124may be connected to one or more support members164extending from one or more surrounding structures, such as the first wall40, the second wall52, a beam, a strut, or some other surrounding structure. Still further, the foam collection cone70may be suspended from a ceiling or other structure above the sump30of the channel24. For example, the foam collection cone70may be suspended in the air via one or more cords, strings, rods, or other suspension mechanisms. Still further, the foam collection cone70may be suspended in the air via magnetism.

Still referring toFIG. 3, a valve166separates the piping82from a pressure regulator (not shown), the valve166being disposed in-line with the removal conduit114, and operable to regulate the pressure within the piping82, thereby allowing for regulation of pressure within a chamber152formed by the cone70and the internal water level150. As illustrated inFIG. 2, the operational water level144, i.e. the water level outside of the cone70, may be above the internal water level150, i.e., the water level inside the cone70. The different water levels are caused by a higher internal pressure of the cone70, which can be caused by the pressure regulator. As a result, the water levels can be different inside of the cone70and outside of the cone70. By changing the pressure within the chamber152of the cone70, the internal water level150can be controlled. For example, by increasing the back pressure within the piping82, the internal water level150is lowered, whereas decreasing the back pressure within the piping82causes the internal water level150to be raised.

Referring now toFIG. 4, a schematic diagram illustrating operation of the system20is shown. The back pressure of the piping82can be controlled with a pressure regulator200. The pressure regulation allows a user to vary the height of the water within the cones70of the devices22to affect foam residence time in the cone70, thereby allowing adjustment for varying water quality conditions. The waste system back pressure can be regulated to adjust the water level in the foam collection cones70thereby making the system flexible for varying water quality conditions. The system20can be expanded by simply adding more foam collection cones70and supporting structure and foam removal piping82. The internal water level150within the cones70may be adjusted up or down based on water quality or based on any other characteristic by restricting the foam waste outlet or regulating back-pressure. As previously discussed, each foam collection funnel104is disposed within one of the foam collection cones70, which increases the velocity of the foam and channels it into the piping system for subsequent removal. In systems20employing more than one foam collection cone70, the internal water levels150within the various collection cones70may be controlled to be the same all at once by means of a single control point of a back pressure valve.

Still referring toFIG. 4, in some embodiments, one or more sensors210may be included within the cone70that may provide feedback to a controller212, which may include a processor and a memory, for determining whether the internal water level150within the cone70needs to be increased or decreased. In some embodiments, feedback from the one or more sensors210may cause the water flow through the channel24to increase or decrease, may cause the amount of bubbles formed within the sump30by the air injectors60to increase or decrease, or cause the back pressure within the piping82to be increased or decreased. For example, any number of sensors may be used, such as an air flow meter, a carbon dioxide sensor, an ammonia sensor, an oxygen sensor, a flow sensor, a mass flow sensor, a depth gauge, a pressure sensor, a level sensor, or any other suitable sensor that can detect a pressure, a water level, a bubble rate, or another measurable characteristic within the system20. In some embodiments, one or more manual controls may be adjusted by a human operator to control the pressure within the piping82. In other embodiments, one or more algorithms implemented by a controller212may be used to control the pressure within the piping82.

The one or more sensors210may be included along any portion of the interior side of the cone70, within the sump30, along the outer surface of the cone70, within the piping82, within the one or more apertures38, along the first portion of the channel24, or at some other point along the path of the water. One or more sensors210may also be provided along portions of the piping82and the removal conduit114that may indicate to a human operator or to the controller212that the pressure needs to be adjusted. In some embodiments, when information is sent from the sensor210to the controller212, the controller212may automatically adjust one or more parameters of the system20. In some embodiments, information from the one or more sensors210is displayed to an operator via a display214such as a graphical user interface or an analog display. In some embodiments, manual controls216are used by a human operator to provide instructions to the controller212as to how to operate parameters of the system20, including the regulation of pressure.

Referring now to the operation of the fractionation device22and toFIGS. 1-4, the internal water level150can be adjusted by applying hack pressure caused by the pressure regulator200downstream of the piping82. The internal water level150may be different than the operational water level144. Preferably, there is no need for an operator to elevate the one or more cones70to adjust foam recovery based on different water qualities since the pressure within the cone can be adjusted via the pressure regulator200. Optionally, the cones70may be raised or lowered, either manually or electronically, to adjust the internal water levels150. The devices22described herein are generally easy to adjust and tune, and an operator can do so simultaneously for multiple cones70. The foam removal turnaround point is internal to the cone70to keep the cones70independent of the piping82. The cones70are removable for ease of cleaning. In some embodiments, the cones70can be removed by uncoupling the one or more connectors122, thereby allowing the one or more cones70to be decoupled from the system20. An operator can wash the inside of the one or more cones by releasing the pressure periodically, thereby allowing water to flow up into the foam collection funnel104.

Once the one or more devices22are installed after cleaning and the system20is operational, water flows from a source, left to right inFIG. 1, along the first portion26of the channel24, between the baffles140, and into the sump30. The water that flows into the sump30then mixes with water already in the sump30. Diffused air is supplied to the sump30via the air release system32attached to the bottom of the sump30. As a result, the water that is in the sump30is subjected to the air bubbles caused by the air release system32. The bubbles travel upward hitting the baffles140, as illustrated inFIG. 2, and are directed into the bottom area of the foam collection cones70. Dirty water is mixed laterally with this upwelling flow. As the bubbles hit the internal water level150in the cone70, foam is generated, and, as it accumulates, it travels up into the cone70above the internal water level150. As the foam reaches the foam collection funnel104, the velocity increases due to the reduced area between the foam collection funnel104and the foam collection cone70. The foam is then forced down the foam collection cone70and drains through the removal piping82to the removal conduit114, and ultimately to waste.

FIGS. 5 and 6schematically depict two additional foam fractionation devices222that may include any components and/or features that are similar to the embodiments disclosed above and may additionally function in the same manner as any of the embodiments disclosed above. Only the differences between the embodiments ofFIGS. 5 and 6and those detailed above will be described. Referring toFIGS. 5 and 6, the foam fractionation device222is shown having a foam collection container270that is generally an inverted cup shape and may include a closed top272, although a portion of the top could be open. In some embodiments, the foam collection container270is made of a flexible material. InFIG. 5, the foam collection container270is shown having an internal water level250that is below an operational water level244and is shown as having at least a portion of the container270above the operational water level244. InFIG. 6, the foam collection container270is shown as having an internal water level250that is below the operational water level244and is shown with the entirety of the foam collection container270submerged below the operational water level244. Both embodiments are depicted as having a foam removal conduit312with an opening314above the internal water level250.

Any of the full flow fractionation systems20and/or full foam fractionation devices22disclosed herein may be utilized within, for example, a recirculating aquaculture system (RAS), that includes any number of other different components, for example, tanks, collectors, filters, mixed bed bioreactors, oxygenators, pumps, disinfectors, or any other suitable components.

It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications, and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. Various features and advantages of the invention are set forth in the following claims.