Patent Application
20220266199
The invention relates seal for use in potting or holding hollow fibre membranes together.
The Membrane Aerated Biofilm Reactor (MABR) or Membrane Supported Biofilm Reactor (MSBR) is one of several types of reactors which uses a submerged membrane module. In the MABR, a gas (usually oxygen in the form of air) is supplied to inside of a hollow fibre membrane and a biofilm is allowed to develop on the other side of the membrane. The biofilm is then used for treating water and or wastewater. The biofilm does this by removing carbonaceous pollutants along with nitrifying/denitrifying the nitrogen-based pollutants, and/or perform xenobiotic biotreatment of the wastewater constituents. The membrane used in the MABR is an air/oxygen/hydrogen (gas) permeable membrane (often a hollow fibre membrane) that provides an interface between the fluid to be treated (fluid phase) and an air/oxygen/hydrogen supply (gas phase). Typically, a biofilm consisting of a heterogeneous population of bacteria (micro-organisms) (generally including nitrifying, denitrifying, and heterotrophic, bacteria) grows on the liquid phase side of the membrane. MABRs can achieve bubble-less aeration and high oxygen utilization efficiency (up to 100%).
Membranes form a barrier between two fluids but allow the passage of specific molecules or particles of specific size between these fluids. It is very important when manufacturing membrane modules that the two fluids are kept apart and that there are no defects in the membranes or in the potting that holds the membranes together and seals the membranes to keep the fluids on either side of the membrane apart.
Membranes can be found in one of three configurations: hollow fibre, flat sheet or spiral wound. Membrane modules are generally found in either tubular or a submerged configuration. In submerged membrane modules, the membranes are generally configured in hollow fibre or flat sheet configurations. With hollow fibre modules, various potting techniques are used to ensure that the membranes are held together and that the fluid inside and outside of the membrane are not in direct communication. In some potting techniques several hollow fibre membranes are brought together into a bunch or an array and a wax or similar material is placed inside the ends of the hollow fibres. The sealed ends are dipped into the potting agent, which is generally a liquid polymer, or the potting agent is poured or placed over and around the ends of the hollow fibre membranes in a mould which gives the potting its required shape. As is described in U.S. Pat. No. 5,639,373, the polymer is allowed to solidify, and it must bond well with the membrane material to ensure that the membranes do not come loose and compromise the integrity of the membrane module. The solidified potting holds the membranes together and allows for membranes to be assembled into the module. Ensuring that the potting agent has wetted each of the hollow fibre membranes is important. The liquid polymer must have a low enough viscosity to flow in between the hollow fibres and bond to the surface. The potting agent must also be chemically compatible with the membrane so that it actively bonds to the surface. Potting of membrane is the most difficult part of membrane module manufacture and is the reason for most membrane module failures.
In a submerged module these potted membranes are connected to a header or manifold by being clamped or adhered to ensure there is a good seal between the potted membranes and the header or manifold, preventing cross contamination between the two fluids. To ensure that a good seal is achieved, an adhesive is used, which bonds with both the polymer of the potting agent and the material of the header, whether that is a polymer or another material such as a metal. This is to ensure that no leaks form over time. In many cases the adhesive is the only method of bonding the potted membranes to the header. Over time the adhesive may weaken or be chemically attacked by chemicals or pollutants in water or wastewater, compromising the integrity of the module. The addition of the adhesive also introduces another step in the manufacturing process. In other instances, a seal or gasket can be placed in between the potted membranes and the header. Using an additional seal creates two material interfaces between the potted membranes and the seal, and between the seal and the header. This leads to leaks and as explained above when adhesives are used, a loss of integrity over time resulting in a failed module.
Submerged membranes modules are often used in wastewater applications where the type of pollutants can vary substantially depending on if the application is a municipal or an industrial wastewater, and concentrations of pollutants can vary from hour to hour depending on environmental or upstream conditions. Conditions can be harsh with temperatures ranging from 4° C. to 40° C. and chemicals such as hypochlorite, acids and bases being used during cleaning procedures. These pollutants in the wastewater and the chemicals used during the cleaning procedures can attack the chemical bonding between the potting and the header, and over time this can become weakened or compromised.
It is the object of the subject invention to overcome at least one of the above-referenced problems.
The invention relates to a potting system used to hold hollow fibre membranes together such that the potting system has an integrated compressive seal. When a mechanical force is used to push the compressive seal against a header or manifold, complete separation is maintained between the fluids inside and outside of the hollow fibre membranes. The potting system can be used in the manufacture of membrane modules suitable for the transfer of dissolved components from one fluid to another.
In one aspect, there is provided, as set out in the appended claims, a potting system (1) comprising a potting unit (2) having a body (3) comprising a distal end (5), a middle section (6) and a proximal end (7), wherein the body (3) further comprises an integrated compressible seal (4) that is continuous with and perpendicular to the body (3), and is composed of the same material as the potting unit (2).
In one aspect, the material is an elastomer. Preferably the elastomer is selected from a polysiloxane, polyurethane, a natural rubber, nitrile rubber, polyisoprenes and fluoroelastomers. Ideally, the elastomer is a polysiloxane selected from silicone, silicone rubber, silicone resin, silicone foam and silicone caulk.
In one aspect, the integrated compressible seal (4) is positioned at a base (9) of the body (3).
In one aspect, the distal end (5) is adapted to accommodate hollow fibre membranes (10) and wherein membranes (10) are potted in the distal end (5) with a potting agent that is the same material as the potting unit (2). Preferably, the distal end (5) is can be any shape selected from circular, a chevron, a cross, linear, square, rectangular, triangular, hexagonal, other polygonal or circular cross-sectional shapes, an ellipse, a three-pointed star, a four-pointed star, a five-pointed star, and the like.
In one aspect, the potting unit (2) is a single piece.
In one aspect, the potting system (1) further comprises a clamp (20).
In one aspect, the clamp (20) comprise a first part (21) and a second part (22) configured to engage with and maintain a downward force on the integrated compressible seal (4) of the potting unit (2). Preferably, the first part (21) comprises a series of spaced-apart hollows (24) which are adapted to accommodate the integrated compressible seal (4) of the potting unit (2).
In one aspect, the second part (22) comprises a series of corresponding spaced-apart hollows (25) which are adapted to accommodate and engage with the middle section (6) of the body (3).
In one aspect, the first part (21) comprises a series of male/female connectors (26) which are adapted to engage with a corresponding series of male/female connectors (27) comprised in the second part (22).
In one aspect, the first and second parts (21,22) each have an additional fastening means (28) at an end (29) thereof.
In one aspect, the potting system (1) further comprises a securing means (30) adapted to engage with the clamp (20) and maintain a downward force on the integrated compressible seal (4) of the potting unit 2. Preferably, the securing means (30) engages with the fastening means (28) at the end (29) of the first (21) or second (22) parts.
In one aspect, the body (2) tapers from the distal end (5) towards the proximal end (7).
In one aspect, the proximal end (7) is adapted to engage with a header (50) of a fluid treatment system.
In one aspect, there is provided a fluid treatment system comprising the potting system (1) described above.
In one aspect, there is provided a Membrane Aerated Biofilm Reactor (MABR), a Membrane Supported Biofilm Reactor (MSBR), a Membrane Bioreactor (MBR), a Membrane Contactor or a Membrane Filtration Unit comprising the potting system (1) described above.
In one aspect, the potting system further comprises a clamp, the clamp comprising a first part adapted to engage with the body of the potting unit and a second part adapted to engage with the integrated compressive seal of the potting unit.
In one aspect, the material of construction of the clamp is suitably a durable yet rigid material, for example polypropylene, polyethylene (PE), polyethylene terephthalate copolymer (PETG), amorphous polyethylene terephthalate (APET), and the like.
One of the advantages of the present invention is that the integrated seal in the potting unit is a mechanical seal that is comprised of material that resists any chemical attack and thus prolongs the life of bunches of fibre membranes in systems such as MABRs and MSBRs or other submerged membrane modules. Another advantage is that the individual potting forms used to secure individual bunches of fibre membranes to the header of such systems permits the user to remove any bunch of membranes, whether they are non-functioning or are a bunch of membranes in need or maintenance, without having an affect on the other bunches of membranes connected to the header within the same system, or without the need for solvent for removing the adhesive or damaging the header through cutting or drilling. Another advantage of the present invention is that it reduces the number of chemicals required in the manufacturing process. The reduction in the number of chemicals used in manufacturing not only reduces cost and complexity, but also reduces the environmental impact of the manufacturing and the health and safety risks to personnel.
In the specification, the term “Membrane Aerated Biofilm Reactor (MABR)” should be understood to mean a Membrane Supported Biofilm Reactor (MSBR) for treating wastewater liquids to remove carbonaceous pollutant removal, nitrify/denitrify the pollutants, and/or perform xenobiotic biotreatment of the wastewater constituents. Soluble organic compounds in the liquid are supplied to the biofilm from the biofilm-liquid interface, whereas gas supply to the biofilm is from the biofilm-membrane interface (by diffusing through the membrane). Typically, a biofilm consisting of a heterogeneous population of bacteria (generally including nitrifying, denitrifying, and heterotrophic, bacteria) grows on the fluid phase side of the membrane. MABRs can achieve bubble-less aeration and high oxygen utilization efficiency (up to 100%) and the biofilm can be separated into aerobic/anoxic/anaerobic zones to simultaneously achieve removal of carbonaceous organic pollutants, as well as nitrification and denitrification in a single biofilm. An example of MABRs of the type comprising a lumen containing a gas phase, a liquid phase, and a gas permeable membrane providing an interface between the gas and liquid phases are described by European Patent No. 2 361 367 (University College Dublin).
In the specification, the term “bunch of membranes” should be understood to mean a collection of from 10 to 100,000, 10 to 10,000, 10 to 1,000 or 10 to 100 gas-permeable, hollow membrane fibres, which are potted at either end into a circular bunch or a shaped element such that the ends of the fibres are open. The membranes can be arranged vertically in the MABR, in which case the resulting liquid flow would be parallel to the membranes, or the membranes could be arranged horizontally in the MABR, resulting in a crossflow configuration.
In the specification, the term “potting unit” should be understood to mean a unit that can be used to secure each membrane together to form a bunch of membranes, which can then be connected to a header or a manifold of a fluid treatment system or membrane module. The potting unit is typically a single, continuous piece made from the same material used as the potting agent.
In the specification, the term “potting agent” should be understood to mean any polymer that is suitable for use with securing fibre membranes in a potting unit. The potting unit can also be composed of the potting agent. A suitable polymer is an elastomer.
In the specification, the term “elastomer” should be understood to mean a polymer having viscoelastic properties (a polymer that displays rubber-like elasticity) and having a high failure strain compared to other non-elastic materials. Examples of elastomer polymers include polysiloxanes (e.g. silicone, silicone rubber, silicone resin, silicone foam or silicone caulk and variants thereof), polyurethane, and rubber (natural rubber or synthetic rubber such as nitrile rubber, isoprene and fluoroelastomers). The elastomer typically has superior sealing properties, stability across a wide temperature range, is durable and resistant to corrosion.
In the specification, the term “fastening means” should be understood to mean a device that closes or secures two or more objects together. Typically, the fastening means creates a non-permanent joint. Examples include cam locks, male/female fasteners, snap fastener, threaded fastener, snap-fit joints and the like.
In the specification, the term “snap(s)” should be understood to mean, as per the industry standard (“The First Snap-Fit Handbook”, 1st Edition, (P. Bonenberger) (2000)) a mechanical joint system where part-to-part attachment is accomplished with locating and locking features (constraint features) that are homogenous with one or the other of the components being joined. Joining requires the (flexible) locking features to move aside for engagement with the mating part, followed by return of the locking feature toward its original position to accomplish the interference required to latch the components together. Locator features, the second type of constraint feature, are inflexible, providing strength and stability in the attachment. Enhancements complete the snap-fit system, adding robustness and user-friendliness to the attachment. The commonest form of snaps is annular (circular connectors), cantilever (hook and recess), and torsional (a latch is attached to a torsion bar or shaft). Snap fits are commonly used as an assembly method for injection moulded parts. The snaps are moulded into the product, so additional parts are not needed to join them together. Additionally, if designed correctly, they can be disassembled and reassembled several times without any problems. A snap fit can either be designed as a permanent snap or a multiple snap. Permanent fits are used in disposable parts that are never meant to be disassembled. Multiple snaps are used in most designs where disassembly for service is expected.
In the specification, the term “distal end” in relation to the potting unit refers to a shaped element or shaped connector and should be understood to mean an element which gives the bunch of membranes a particular shape (e.g. chevron shaped, cross-shaped, linear, square, rectangular, triangular, hexagonal, other polygonal or circular cross-section etc.). This provides a connector end that can be secured in a gas-tight manner to the upper or lower manifolds (or headers), which then become known as potted membranes.
In the specification, the terms “upper manifold” and “lower manifold” should be understood to mean gas manifolds (or headers) which are equipped with ports designed to receive the potting unit, which encompass the bunches of hollow fibre membranes. In addition, a plurality of potting units may be potted directly into the upper and lower gas manifolds to form a continuous bunch of membranes stretching from one end of the manifold to the other. When oriented vertically the top manifold is referred to as the upper manifold and the bottom manifold is referred to as the lower manifold. The upper and lower manifolds are in fluid communication with the internal architecture of all the hollow fibres such that air/gas can flow from the inside of the upper manifold, through the hollow fibres to the lower manifold, or vice versa.
In the specification, the term “membrane module” or “Membrane Aerated Biofilm Reactor (MABR)” should be understood to mean a device into which a number (2-1,000, 2-900, 2-800, 2-750, 2-700, 2-650, 2-600, 2-550, 2-500, 2-450, 2-400, 2-350, 2-300, 2-250, 2-200, 2-150, 2-100, 2-50) of cassettes consisting of hollow fibre membranes can be secured in parallel. The cassettes are generally secured in a frame.
In the specification, the term “fluid” should be understood to mean a liquid or gas, where the liquid can be any such form such as water or wastewater, which should be understood to mean any water that has been adversely affected in quality by anthropogenic influence. Wastewater can originate from a combination of domestic (for example, sewage), industrial, commercial or agricultural activities, surface runoff or stormwater, and from sewer inflow or infiltration.
The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:
The invention described herein provides a potting system for use in the manufacture of a fluid treatment system, such as a MABR or MSBR, Membrane Bioreactors (MBRs, which are used for wastewater treatment), Membrane Contactors for gas delivery or gas removal (typically found in the beverage industry or chemical industry), and Membrane Filtration Units (which can be used in the chemical, pharmaceutical, or food and beverage industry), the system comprising a potting unit and, optionally, a clamp. The potting unit is typically a single piece composed of a potting agent, the same potting agent that is used to secure a bunch of hollow fibre membranes to a potting unit. The potting unit also comprise an integrated compressible seal that is resistant to attack from chemicals or other reagents that may be found within the liquid being treated and also provides a mechanical seal within the treatment system to ensure that liquid either side of the membranes do not mix.
Turning now to the Figures, wherein
The distal end 5 is adapted to accommodate a bunch of hollow fibre membranes 10, which are potted into the potting unit 2 using a potting agent. The potting unit 2 is typically a continuous piece made from the same potting agent used to secure the hollow fibre membranes 10 in the distal end 5 of the potting unit 2. The potting agent also creates the shape of the integrated compressible seal 4. The distal end 5 around the membranes 10 can acts as a connector that can be shaped in a particular manner (a shaped connector) to space out the membranes 10 to form unique shapes or patterns, such as that described in EP3297749. Alternatively, the distal end 5 can be cylindrical in nature.
In addition, the integrated compressible seal 4 can also be manufactured to any shape that is desired, such as circular, a chevron, a cross, linear, square, rectangular, triangular, hexagonal, other polygonal or circular cross-sectional shapes, an ellipse, a three-pointed star, a four-pointed star, a five-pointed star, and the like.
The proximal end 7 typically has connectors 8 that are configured to engage with a header 50 (see
Membranes used in the MABR are in most cases dense membranes. These membranes do not have pores but instead allow the diffusion of gas molecules through their the inter polymeric lattice. The most common materials used are Poly DiMethyl Siloxane (Silicone) or Poly Methyl Pentane. Silicone is often used in non-stick applications due to its low surface energy as well as being used in seals and gaskets due it being elastic and compressible, which can be stretched around a nozzle or nipple and compressed between two surfaces.
Because of silicone's properties it is not always easy to bond to other materials and therefore silicone is often used as the potting agent for silicone membrane because silicone will adhere to itself and it can be chemically bonded to each membrane. Most other potting agents are not compressible once solidified and therefore are not suitable for forming a mechanical seal as set out by the claimed invention. By forming the potting silicone around the membranes in such a manner as to have an integrated seal, mechanical clamps can then be used to keep the potted membranes attached to a header. By forming the potting in such a shape, the potting material can have a compression seal and thus avoids the requirement to bond the potted membranes to a header to ensure complete separation of the fluids on either side of the membrane. The compressive force used on the mechanical seal should be enough to keep the potted membranes in place, but not excessive as to damage the potting silicone and cause tears in the potting silicone. The elastomer used for potting the membranes should be of a similar bond length and use a similar same catalytic cross-linking procedure as that used for forming the hollow fibre membranes to ensure chemical compatibility. The elastomer used for forming the potting should also have the same shore hardness as the polymer used to produce the membranes.
In the specification the terms “comprise, comprises, comprised and comprising” or any variation thereof and the terms “include, includes, included and including” or any variation thereof are considered to be totally interchangeable and they should all be afforded the widest possible interpretation and vice versa.
The invention is not limited to the embodiments hereinbefore described but may be varied in both construction and detail.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19193478.5 | Aug 2019 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/073199 | 8/19/2020 | WO |
