FIELD

[0001] This invention relates generally to reverse osmosis, ultrafiltration, nanofiltration or microfiltration separation devices and more particularly to spiral wrapped membrane elements and the manner in which they are loaded into pressure vessels.

BACKGROUND

[0002] As shown in Figure 1, a spiral wound membrane element (1) is constructed by wrapping one or more membrane leaves (2) and feed spacer sheets (3) around a perforated central permeate collection tube (5). The membrane leaves have a permeate carrier sheet (4) placed between two generally rectangular membrane sheets. The membrane sheets are sealed together along three edges. The fourth edge of the leaf is open and abuts the central tube. One or more layers of permeate carrier sheet may also be wrapped around the central tube to support the membrane leaf over the perforations in the central tube and to provide a flow path between the edge of the leaf and the central tube. Product water, also called permeate, passes through the membrane sheets and then flows through the permeate carrier sheet to reach the central tube. The membrane element is surrounded by a protective outer wrap (6) that keeps the element from un-wrapping. Anti-telescoping devices (7) cap each end of the element and the upstream anti- telescoping device typically has a circumferential brine seal which aids in channeling the feed flow through the element.

[0003] The current industry standards use spiral wrapped elements with an outside diameter of 8 inches, although numerous applications use 4, 6, 10 12 or 16 inch diameter elements. A typical 8 inch diameter spiral wrapped membrane element weighs 30-40 lbs. As shown in Figure 2, cylindrical pressure vessels (10) used in spiral wrapped membrane applications each typically hold 6 to 8 membrane elements (1) in a series arrangement with the feed end of each element connected to the concentrate end of the preceding element. Permeate tubes (5) are connected using permeate connectors (13).

[0004] The pressure vessels are typically cylindrical in shape with the interior diameter slightly larger than the exterior diameter of the membrane element. Either end of the pressure vessel may have features passing through the walls, such as ports, or interior features such as grooves for retaining rings. The central part of the pressure vessel, where the membrane elements are placed in their final loaded position is typically a uniform featureless tube. While some pressure vessels are designed to have the feed, brine and permeate ports pass through the end caps of the pressure vessel, some have feed and brine ports that pass through the side walls near the ends of the pressure vessel.

[0005] When the spiral wound membrane elements are loaded into the cylindrical pressure vessel, it is typically a manual operation with each element being inserted concentrate or downsteam end (9) first into the open feed or upstream end (11) of the pressure vessel. The process advocated by membrane element manufacturers are strikingly similar as documented in GE ^® TBI 157 (July 2015), Dow ^® Form No. 609-02069-0611, Hydronautics ^® TSB122.06 (June 2015) and the Toray ^® Operation, Maintenance and Handling Manual (rev 106). As elements are inserted, they are manually pushed into the pressure vessel, each successive element moving all previously inserted elements along the length of the pressure vessel until they reach their final loaded positions. With each successive element inserted, additional force must be applied to move the mass of the elements as well as overcome the friction between the brine seals of the element structures and the interior diameter of the cylindrical pressure vessel. For large commercial systems, the insertion of the final elements requires significant force to move all previously inserted elements along the interior length of the pressure vessel. This force often exceeds the force that may be applied manually.

INTRODUCTION

[0006] As systems grow larger, the length of the cylindrical pressure vessels may grow as well as the number and/or size and weight of the elements they contain. There is currently a need for a method of simplifying the loading of spiral wrapped membrane elements which will reduce or eliminate the need to apply large forces to move membranes into and along the length of the cylindrical pressure vessel.

[0007] This specification describes a method, and a system for loading spiral wrapped membrane elements into a cylindrical pressure vessel. The method describes how spiral wrapped membrane elements may be loaded and positioned in their loaded positions, individually and sequentially. The system describes the three components of the system; a seal for the first end of the pressure vessel, a movable seal for inserting spiral wrapped membrane elements, and a vacuum source for drawing the individual membrane elements into the pressure vessel and seating them in their final loaded positions.

[0008] The detailed embodiment that is described comprises a removable plug fitted into one end of the pressure vessel, an insertion tool which is inserted into the cylindrical pressure vessel at the end opposite the plug after the insertion of a spiral wrapped membrane element, and a vacuum source which is used to evacuate the air from the space between the plug and the insertion tool. BRIEF DESCRIPTION OF THE FIGURES

[0009] Figure 1 shows a typical spiral wrapped membrane element.

[0010] Figure 2 shows a cross section of a typical cylindrical pressure vessel loaded with spiral wrapped membrane elements installed in series.

[0011] Figure 3 shows one embodiment of a removable plug with a port for the vacuum source to be attached.

[0012] Figure 4 shows a cross section of the removable plug embodiment of Figure 3, detailing the vacuum feed-through.

[0013] Figure 5 shows a section detail of a first end of the cylindrical pressure vessel with removable plug embodiment of Figure 3 installed and a first spiral wrapped membrane element seated in its final loaded position.

[0014] Figure 6 shows one embodiment of a removable insertion tool with a flexible line attached.

[0015] Figure 7 shows a section detail of a second end of the cylindrical pressure vessel with a spiral wrapped membrane element and the removable insertion tool embodiment of Figure 6, where the circumferential seal of the removable insertion tool has engaged with the inside diameter of the cylindrical pressure vessel to create an essentially air tight volume.

[0016] Figure 8 shows a section view of the cylindrical pressure vessel with the removable plug embodiment of Figure 3 installed, two spiral wrapped membrane elements in their loaded position, and a third spiral wrapped membrane element with the removable insertion tool embodiment of Figure 6 in transit along length of the pressure vessel.

DETAILED DESCRIPTION

[0017] This invention describes a method and system for inserting spiral wrapped membrane elements into a pressure vessel and moving them to their loaded positions. This invention uses a pressure differential created between atmospheric pressure and an artificial pressure created inside of the pressure vessel to cause individual elements or groups of elements to translate along the interior length of the pressure vessel until they achieve their loaded position and

configuration. This invention comprises three primary elements; a stationary seal applied to one end of the pressure vessel, and a movable seal that is removably attached to the membrane element or elements being inserted into the pressure vessel and a vacuum or pressure source. An essentially airtight volume is created within the pressure vessel between the stationary seal and the movable seal. One or both of the seals have a feed through in fluid communication with both the vacuum source and the essentially airtight volume. The source of vacuum or pressure is used to create an artificial pressure different than atmospheric pressure within the essentially airtight volume. The artificial pressure in the essentially airtight volume creates a pressure differential with atmospheric pressure and results in an unbalanced force on the movable seal. This unbalanced force causes the movable seal along with at least one membrane element to translate along the length of the pressure vessel. When the at least one membrane element reaches its loaded position within the pressure vessel, the artificial pressure is released, removing the pressure differential and causing the movable seal to disengage from the at least one membrane element to which it was attached. The removable seal can then be removed from the pressure vessel. This method and system can be repeated to sequentially load a full complement of membrane elements into a single pressure vessel.

[0018] Embodiments of this invention may be configured to use either pressure of vacuum to as the artificial pressure in the essentially airtight volume. The preferred embodiment discussed in the remainder of this description uses vacuum to create the force required to move the membrane elements into their loaded position in the pressure vessel.

[0019] This invention uses a vacuum source to create a pressure differential inside of a cylindrical pressure vessel. Atmospheric pressure is then used to push a movable seal attached to an individual spiral wrapped membrane element into the cylindrical pressure vessel and seat them in a loaded position. One embodiment of the system is comprised of three main

components; a removable plug assembly, a removable insertion tool, and a vacuum source. It is anticipated that this invention can be applied to all variants of construction, components and materials for membrane elements that are designed to function in a series arrangement inside of a cylindrical pressure vessel.

[0020] Figure 1 shows the construction of a typical spiral wrapped membrane element (1) that is used in purification of fluids. The components, construction and operation of spiral wrapped membrane elements are well known to those skilled in the art. The element is comprised of one or more membrane sheets (2) with feed channel spacers (3) and permeate collection material (4) wrapped around a central permeate collection tube (5). The outer surface of the element is wrapped in a protective material (7) to ensure stability of the element. Anti- telescoping devices at either end of the element (7) maintains the configuration and stability of the spiral wrapped element. The upstream anti-telescoping device typically has a circumferential seal (brine seal) that engages with the interior diameter of the cylindrical pressure vessel and ensures proper flow of the feed fluid through the membrane element. Each spiral wrapped membrane element has a feed end (8) where raw fluid enters the element, and a concentrate end (9) where concentrated fluid, also known as brine, exits the element. [0021] The spiral wrapped membrane element is designed to operate inside of a cylindrical pressure vessel. Larger systems operate with a number of spiral wrapped elements loaded in series inside of single pressure vessel as shown in Figure 2. The cylindrical pressure vessel (10) has a feed end (11) where raw fluid enters the pressure vessel and a concentrate end (12) where concentrated fluid or brine leaves the pressure vessel. The permeate tubes (5) of individual spiral wrapped elements (1) are connected in fluid communication with each other using a permeate connector (13). The feed passes from element to element within the pressure vessel. As the feed passes through each element, a portion of the fluid passes through the membrane to become permeate, the remaining fluid exits the vessel as concentrate. The description of this invention will focus on the loading of spiral wrapped membrane elements concentrate end (9) first into the feed end (11) of the pressure vessel as this is the current industry standard. This is so the brine seals retain their proper configuration as the element moves along the length of the pressure vessel to reach its final operating position. It is anticipated that this invention could be used to insert spiral wrapped membrane elements from either the feed end or the concentrate end of the pressure vessel as allowed by the brine seal and element design.

[0022] Figure 3 shows one embodiment of the removable plug assembly (20). In this embodiment, the removable plug is comprised of four basic features; a circumferential seal (21), a body that extends into the pressure vessel (22), a feed-through for the vacuum source (23), and restraint bars (24). In this embodiment, the circumferential seal (21) engages with the interior diameter of the pressure vessel. The removable plug creates one end of an essentially air tight volume within the pressure vessel as shown in Figure 5. It is anticipated that this seal will not be completely air tight, and a certain amount of leakage through the seal can be tolerated without adversely affecting the function of the invention. In this embodiment, the plug is inserted into the concentrate end of the cylindrical pressure vessel and a retaining ring (25) is inserted into the pressure vessel as shown in Figure 5 to position the exterior face of the plug. The retainer ring is a standard part of the pressure vessel assembly and is used in operation to hold the end caps of the pressure vessel in place. Threaded members (26) pass through restraint bars (24) that engage with the end face of the pressure vessel as shown. In this embodiment, threaded wing nuts are attached to the threaded members and tightened. In this manner, the plug is securely positioned in the pressure vessel by the combination of the retaining ring and the restraint bars, and will not be drawn into the pressure vessel by vacuum, or expelled from the pressure vessel by the spiral wrapped elements as they are positioned within the pressure vessel.

[0023] As shown in Figure 5, this embodiment of the plug extends into the cylindrical pressure vessel to a predefined position providing a hard stop for a first spiral wrapped membrane element (27) inserted. This hard stop places the first element at its loaded position and defines the loaded position of each subsequent element inserted into the pressure vessel. This loaded position of the membrane element is within an acceptable dimensional tolerance of its final operation position within the pressure vessel and is the equivalent of the positioning that is currently achieved using manual insertion methods. In this embodiment, the circumferential seal (21) is inserted past the port (28) on the side of the pressure vessel to define the non-movable end of the essentially airtight volume within the pressure vessel.

[0024] In this embodiment, a feed through for a vacuum source (23) is provide in the plug. This feed through connects the exterior vacuum source (29), described below, with the essentially airtight volume defined within the cylindrical pressure vessel and is of sufficient diameter to create and maintain a negative pressure within the essentially airtight volume as will be described in greater detail below.

[0025] In this embodiment of the invention, restraint bars (24) fastened to the plug body by threaded rods (26) and nuts to position the plug body and prevent the plug from being drawn into the cylindrical pressure vessel by the applied vacuum. Numerous other methods of attaching the plug to the end of the pressure vessel are envisioned. These include, but are not limited to ring assemblies, plate assemblies and clip arrangements that engage with the body of the plug assembly with clips, bolts, straps, springs or other attachment methods known in the art. It is also envisioned that the removable plug assembly may be constructed in a manner that an integral shoulder feature is present that may engage with the pressure vessel minimizing the need for additional parts.

[0026] The removable insertion tool is a movable, essentially airtight seal that seals an end of a membrane element and may also create a seal with the inner diameter of the pressure vessel. The embodiment of the removable insertion tool (40) depicted in Figure 6 is a solid body with a circumferential seal (41) that is an appropriate diameter to engage with the inside diameter of the cylindrical pressure vessel (10) and allow translation of the tool along the length of the pressure vessel In one embodiment of the insertion tool, the outer circumference of the body is an appropriate diameter to engage with the inner diameter of the pressure vessel and create the circumferential seal (41). In other embodiments, a seal structure such as an o-ring or a brine seal may be disposed on the outer circumference of the body to create the circumferential seal (41) to ensure the proper engagement with the inner diameter of the pressure vessel. The body of the insertion tool is of solid construction with a diameter at least as large as the outer diameter of the membrane element. When the insertion tool bears against the membrane element an essentially airtight seal is created on the face of the spiral wrapped element and the feed end of the permeate tube. In another embodiment of this invention, the insertion tool's only function is to seal the permeate tube and feed end of the spiral wrapped membrane element. In this embodiment, the brine seal of the membrane element provides a sufficient seal with the interior diameter of the pressure vessel to create the essentially airtight volume. The embodiment of the removable insertion tool depicted in Figures 6-8 is designed to engage with the feed end of a spiral wrapped membrane element and has a recess (42) to accommodate a permeate connector extending from the permeate tube on the feed end of the element. The face of the insertion tool opposite the face that engages the spiral wrapped element further comprises an attachment point (43) for a flexible line, and a flexible line (44) attached to the insertion tool. The flexible line may comprise one or more of a rope, a cable, a strap, a vacuum hose and/or a vacuum tube. A length of flexible line greater than the length of the pressure vessel allows convenient retrieval of the insertion tool. The attachment of the flexible line to the insertion tool may be any of the vast number of attachment methods that are well known for securely fastening flexible lines to attachment points. In the depicted embodiment, an eye bolt is used as the attachment point.

[0027] It is anticipated that the insertion tool may also be retrieved from the interior of the pressure vessel through the application of pressure to the essentially airtight volume. This would reverse the pressure differential and move the insertion tool back to the open end of the pressure vessel.

[0028] When the insertion tool (40) and element (1) are inserted into the feed end (11) of the cylindrical pressure vessel (10) and advanced to the point where the insertion tool engages with the inside diameter of the pressure vessel as shown in Figure 8, an essentially airtight volume (50) is created within the pressure vessel. It is to be noted that a certain amount of air leakage around the seal is to be expected, and a certain amount of leakage past the seal can be tolerated without adversely affecting the function of the invention. In the depicted embodiment of the invention, the permeate connector (13) is inserted in the permeate tube (5) on the feed end of the spiral wrapped membrane element and the insertion tool is designed with a recess (42) to accommodate the protruding connector. It is anticipated that the permeate connector could be inserted into the concentrate end of the spiral wrapped membrane element prior to insertion of the element into the pressure vessel and in this case, the insertion tool would not require an accommodation for the permeate connector. The circumferential seal on the insertion tool (41) is designed in a manner so that the tool may freely translate in either direction inside of the cylindrical pressure vessel while maintaining the essentially airtight volume (50).

[0029] In this embodiment, the vacuum source (29) attaches to the vacuum feed through as depicted in Figure 4 and may be any of a number of options that provide sufficient vacuum to create a pressure differential between atmospheric pressure and the essentially airtight volume (50) defined by the walls of the pressure vessel (10), the removable plug (20) and the insertion tool (40). In one embodiment, a Dayton Model 4YE62 commercially available shop vacuum is used as the vacuum source with its vacuum hose attached to the vacuum feed through of the plug. In this way, the vacuum source is connected in fluid communication with the essentially airtight volume and is capable of creating a pressure different than atmospheric pressure within the essentially airtight volume. In this embodiment of the invention, the pressure different than atmospheric pressure is a partial vacuum. The vacuum source should be capable of creating sufficient suction to draw the spiral wrapped element and insertion tool into and along the length of the cylindrical pressure vessel, however the vacuum should not drop below 0.1 atmosphere, as this may damage the membrane element. The vacuum source, the plug or the removable insertion tool may optionally be equipped with a pressure control device (30) in fluid

communication with the essentially airtight volume (50) to ensure a maximum vacuum level is not exceeded. The pressure control device may be a valve, a relief valve, a pressure regulator or a pressure sensor coupled to the vacuum source. The optional pressure control device may also be used to adjust the pressure differential and therefore the translation speed of the element as necessary.

[0030] The following non-limiting example illustrates how the described embodiment of this system and method are used to load spiral wrapped membrane elements into a properly prepared pressure vessel. In this example, the spiral wrapped elements are loaded from the feed end of the pressure vessel. Loading from the feed end predefines the orientation in which the elements are loaded, in this case concentrate end first. Alternatively, loading elements into the concentrate end of the pressure vessel would predefine the loading orientation of the membrane elements to be feed end first. First, the removable plug (20) is inserted in the concentrate end (12) of the pressure vessel (10), and the retainer ring (25) is inserted to maintain the plugs position. The restraint bars (24) are attached to the outer face of the plug via threaded rods (26) and nuts. The nuts are tightened on the threaded rod so that the restraint bars are brought into contact with the concentrate end of the cylindrical pressure vessel and the plug is in contact with the retainer ring. A Dayton Model 4YE62 commercially available shop vacuum is used as the vacuum source. The vacuum hose of the vacuum source (29) is then attached to the vacuum feed through (23) on the plug so that it is in fluid communication with the interior of the cylindrical pressure vessel.

[0031] A first spiral wrapped membrane element (1) is prepared for insertion into the cylindrical pressure vessel. This may include the steps of inserting a permeate connector (13) into the feed end of the permeate collector (5) on the feed end (9) of the spiral wrapped membrane element. This connector may be installed on the feed end of each membrane element as it is inserted into the pressure vessel, or alternatively, it may be installed on the concentrate end of each element as it is installed in the pressure vessel. Alternatively, a permeate connector may be an integral part of the spiral wrapped membrane element, in which case the insertion of an additional part is un-necessary. A lubricating material may be applied to the contact points of the spiral wrapped element, such as the brine seals and permeate connectors to reduce the force necessary to move the spiral wrapped element along the interior length of the cylindrical pressure vessel, and reduce the forces necessary to engage the permeate connectors of adjacent elements. The prepared membrane element, with optional lubricant applied and permeate connector inserted as appropriate, is then inserted concentrate end first into the feed end of the cylindrical pressure vessel.

[0032] The spiral wrapped membrane element (1) is inserted into the cylindrical pressure vessel until the brine seal of the feed end of the membrane element engages with the inside diameter of the cylindrical pressure vessel, and then advanced into the pressure vessel an appropriate distance to an initial starting position. The pressure vessel may have side ports (28) for the feed to enter and concentrate to exit, in which case the membrane element may be advanced to an initial starting position where the seal (41) of the insertion tool (40) is beyond the feed port as depicted in Figure 7. The insertion tool may be fitted to the feed end of the membrane element at any convenient point as the element is prepared or initially inserted into the pressure vessel. The insertion tool may also be attached to the membrane element after the membrane element has been inserted into the pressure vessel and advanced to its initial starting position.

[0033] When the element and insertion tool have been inserted to the initial starting position, an essentially airtight volume (50) is created between the plug (20), the walls of the pressure vessel (10) and the insertion tool (40). At this point the vacuum source (29) may be engaged to reduce the air pressure within the essentially airtight volume and create a pressure differential between atmospheric pressure on the outside of the insertion tool and the essentially airtight volume. The pressure differential will cause an unbalanced force to be exerted on the insertion tool. This in turn, will cause the insertion tool and the attached membrane element to be drawn into and along the length of the cylindrical pressure vessel as depicted in Figure 8. Optionally, tension on the flexible line attached to the insertion tool may be used to control and monitor the movement of the tool and element along the length of the cylindrical pressure vessel. This tension may be applied manually. Vacuum is maintained on the essentially airtight volume until the membrane element is seated in its loaded position. For the first spiral wrapped membrane element inserted into the pressure vessel (27), this position will be defined as the position where the concentrate end of the element reaches the hard stop created by the plug as depicted in Figures 5 and 8. For subsequently inserted membrane elements, the loaded position will be defined as the position where the permeate connector has completely engaged the permeate tube of the inserted element and the permeate tube of the prior inserted element.

[0034] When the inserted element has reached its loaded position, the vacuum source is terminated and the pressure inside of the essentially airtight volume is returned to atmospheric pressure. This will cause the insertion tool to disengage from the inserted spiral wrapped membrane element so that the insertion tool can then be retrieved from the interior of the pressure vessel by drawing it out with the flexible line. Alternatively, air pressure could then be applied through the vacuum feed-through to force the insertion tool back out of the pressure vessel.

[0035] The steps of preparing the membrane element, inserting the element into the pressure vessel, positioning using the vacuum source and retrieving the insertion tool may be repeated as many times as necessary to load a full complement of membrane elements into the pressure vessel.

[0036] In one embodiment of this invention, multiple membrane elements may be loaded at once. The multiple membrane elements, which are a subset of the full complement of membrane elements required by the pressure vessel, may be loaded into the pressure vessel, with the appropriate permeate connection between the elements. The insertion tool is attached to the feed end of the final membrane element to be inserted, and the subset of membrane elements are then drawn into their loaded position simultaneously by the vacuum source.

[0037] It is noted that the vacuum source and insertion tool may not be required for the insertion and placement of the last several elements, as the force required to move a small number of properly prepared elements into the pressure vessel is within the abilities of a single operator.

[0038] When the pressure vessel has been loaded with a full complement of spiral wrapped membrane elements, the plug must be removed by first removing the retaining bars, removing the retainer ring and then extracting the plug from the concentrate end of the pressure vessel. When the components of the insertion system have been removed, the loaded pressure vessel may then be prepared, sealed and tested per known processes and placed into or returned to operation.

[0039] By way of one or more of methods described herein, membrane elements are moved in a pressure vessel comprising by applying air pressure to a sealed end of the membrane element after inserting the membrane element into an open end of a pressure vessel. [0040] By way of one or more methods described herein, a membrane element is loaded in a pressure vessel. The membrane element is inserted into a first end of the pressure vessel and a partial vacuum is created in a second end of the pressure vessel effective to move the membrane element towards the second end of the pressure vessel.

[0041] By way of one or more methods described herein, spiral wrapped membrane elements are loaded into a cylindrical pressure vessel. A first end of the cylindrical pressure vessel is sealed. A spiral wrapped membrane element is inserted into a second end of the pressure vessel. A pressure differential is created acting on the spiral wrapped membrane element thereby moving the spiral wrapped membrane element to a final operating position in response to the pressure differential. The pressure differential is later removed.

[0042] The steps used to load one element may be repeated to sequentially load additional spiral wrapped membrane elements into the pressure vessel. Optionally, a subset of spiral wrapped membrane elements is loaded into said pressure vessel and moved to a final operating position before moving another subset of the elements into their operating position. Optionally, the pressure differential may be created by a vacuum source. Optionally, the said first end of the cylindrical pressure vessel is the concentrate end and the said second end of the cylindrical pressure vessel is the feed end. Optionally, the concentrate end of said spiral wrapped membrane element is loaded into the feed end of said pressure vessel.