Bypass control sleeve for hygienic spiral filters

Abstract

The bypass control sleeve has circumferential protrusions along its outer surface. The protrusions of the bypass control sleeve may be distributed along the length of the sleeve with constant diameter portions of the sleeve in between. The protrusions may be asymmetric and / or have a steep and / or concave curved front surface. A method of making the bypass control sleeve includes molding the protrusions on the outer surface of the sleeve. A method of installing the bypass control sleeve includes sliding the sleeve over the end of a spiral-wound membrane element. The combination of the bypass control sleeve secured to the spiral-wound membrane element may be installed in a pressure housing.

Description

Technical Field

[0001] The present disclosure relates to spiral membrane elements, for example spiral membrane elements that can be used for hygienic applications.

Background Art

[0002] The following considerations do not admit that what is considered below can be cited as prior art or common general knowledge.

[0003] Spiral membrane elements enable the filtration or separation of a feed solution. The feed solution may contain, for example, dissolved or dispersed ions, organic substances, proteins, microorganisms and / or suspended solids. Spiral membrane elements typically have a plurality of layers wound around a perforated central tube. One winding layer forms a membrane leaf comprising two halves of adjacent folded membrane sheets separated by an internal permeate collection material (permeate carrier sheet). A feed spacer sheet is disposed within the fold of each membrane sheet. Glue lines seal the permeate carrier sheet between adjacent membrane sheets along three edges of the membrane leaf. The fourth edge of the leaf remains open to the perforated tube. In use, the spiral membrane element separates the feed solution into a permeate (also known as filtrate or effluent) and a concentrate (also known as retentate or brine).

[0004] The spiral membrane element is housed in a pressure housing, also referred to as a pressure tube or pressure vessel. Pressurized feed fluid is delivered at the upstream end of the pressure housing and flows into the ends of the spiral membrane element, specifically the edges of the feed spacer sheet, and possibly around the outside of the element. Within the spiral membrane element, the pressurized feed material flows across the surface of the membrane sheet through the feed spacer sheet. The membrane sheet may have a separation layer of a size suitable for microfiltration, ultrafiltration, nanofiltration, or reverse osmosis. A portion of the pressurized feed material is carried through the separation layer by membrane penetration pressure, generating a permeate flow. The permeate flow flows along the permeate carrier sheet into a central perforated tube and then through the central tube to the outlet at the end of the pressure housing. Components of the pressurized feed material that do not pass through the membrane, i.e., retaining fluid, continue to move through the feed spacer sheet and are collected at the downstream end of the pressure housing.

[0005] The outer diameter of the membrane element is typically several millimeters smaller than the inner diameter of the pressure housing. An annular space exists between the inner surface of the pressure housing and the outer surface of the spiral membrane element. The annular space is a low-flow region, also called a narrow tolerance. Some of the feed material can pass through the annular space. This is called bypass flow. In the narrow tolerance region, fluid access is restricted, and therefore cleaning for removing solids or providing disinfectant solution is limited. Increasing bypass flow improves cleaning of the annular space. However, bypass flow also reduces the volume of feed material that passes through the spiral membrane element and contributes to permeate generation. In some cases, the membrane element has an impermeable outer wrap and brine seal between the outer wrap and the pressure housing to completely block or seal the annular space to prevent bypass flow. Preventing bypass flow can improve permeate generation by pushing more feed material into the membrane element, but feed material may accumulate in the annular space. The fluid in the annular space may communicate with the feed channel through the portion of the feed spacer exposed to the annular space.

[0006] In certain industries, spiral membrane elements are required to intentionally provide some bypass flow. For example, membrane elements in the dairy industry must meet the requirements of the Sanitary 3A standard for cross-flow membrane modules. Meeting these standards requires some bypass flow to flush out the annular space. Membrane elements used in these industries are referred to as sanitary modules or sanitary elements. Some examples of sanitary elements are described in U.S. Patent Nos. 5,985,146, 7,208,808, 8,668,828, and 8,940,168. Sanitary modules also typically have a cage around the membrane leaves. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent No. 5,985,146 [Patent Document 2] U.S. Patent No. 7,208,808 [Patent Document 3] U.S. Patent No. 8,668,828 [Patent Document 4] U.S. Patent No. 8,940,168 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Typically, two or more spiral membrane elements are housed in a single pressure housing. For example, in the dairy industry, five or six spiral membrane elements may be housed in a single pressure housing. The central tubes of the membrane elements in the pressure housing are connected in series, and the feed material also passes through the membrane elements in the housing in approximately series. In a complete system, many pressure housings may be present. The pressure housings are typically oriented horizontally on racks, which can reach heights of up to 10 m. Occasionally, membrane elements are removed from the pressure housing and replaced with new ones. This is generally done by sliding the membrane elements in and out of the pressure housing while the pressure housing remains installed on the rack. However, certain brine seals may make it difficult to slide the membrane elements in and out of the pressure housing. [Means for solving the problem]

[0009] This disclosure describes a bypass control sleeve for a spiral membrane element, a method for fabricating a bypass control sleeve, and a method for installing a bypass control sleeve. The outer surface of the bypass control sleeve may have one or more of the following: asymmetrical projections, projections separated by segments of a constant diameter, and projections having a steep or concave front surface. In at least some examples, the bypass control sleeve provides sufficient turbulence to provide sanitary conditions in the annular space around the bypass control sleeve with low bypass flow. The bypass control sleeve may be provided at one or both ends of the spiral element along only a portion of the length of the spiral element. The bypass control sleeve may be made of a pre-formed material to provide projections, or it may slide on the end of the spiral element. [Brief explanation of the drawing]

[0010] [Figure 1A] This figure shows a cross-section of a conventional bypass control sleeve design, which has a rounded peak. [Figure 1B]This figure shows a partial cross-section of a conventional bypass control sleeve design with a triangular peak. [Figure 2] This figure shows a portion of the surface of a novel bypass control sleeve, optionally called an asymmetrical peak or curved peak sleeve, which has an asymmetrical peak, a steep, concave peak front, and a valley separating the peak. [Figure 3A] This figure shows a bypass control sleeve, as shown in Figure 2, fixed to the end of a spiral-type membrane element. [Figure 3B] This figure shows a bypass control sleeve, as shown in Figure 2, that extends along the entire length of the spiral-type membrane element. [Figure 4] Figure 2 shows a flow rate comparison graph between conventional bypass control sleeves (triangular and rounded) and bypass control sleeves (curved peak). [Figure 5] Figure 2 shows a comparison of the cell Reynolds numbers determined by computational fluid dynamics, illustrating the flow velocity of conventional bypass control sleeves (triangular and rounded) and bypass control sleeves (curved peak), as shown in the figure. [Figure 6] This is a schematic diagram of the bypass control sleeve test system. [Figure 7] This graph shows the supply flow at a specific pressure drop in a spiral membrane module with triangular and curved peak sleeves. [Figure 8] This graph shows the housing flow in gpm relative to gallons of generated RO permeate at 10 psid for both triangular and curved peak shells. [Figure 9] This graph shows the recirculation pump output in kW against the %Brix of the feed solution for both triangular and curved peak shells, respectively. [Modes for carrying out the invention]

[0011] A spiral membrane element equipped with a bypass control sleeve, which may also be referred to as a bypass control ring, is described herein. The bypass control sleeve is a sleeve configured to fit around the spiral membrane element. The bypass control sleeve disrupts the flow of feed material in the annular space between the outside of the spiral membrane and the inner wall of the pressure vessel. Disrupting the flow of feed material outside the element generates turbulence that helps to clean the annular space and reduce the overall bypass flow rate.

[0012] Figures 1A and 1B illustrate some of the prior art bypass sleeve or ring designs having protrusions. Figure 1A shows a protrusion having a rounded or convex circular peak design 102, while Figure 1B shows a protrusion having a pointed or triangular peak design 104. Both prior art designs provide a symmetrical peak shape. The rounded peak design 102 in Figure 1A has short valleys 106 between adjacent protrusions, the valleys containing a portion of the sleeve having a constant diameter along its width. The valleys 106 of the rounded peak design have a width of less than 50% of the width of the protrusion 108. The design in Figure 1B includes adjacent protrusions 110, 112 that intersect at point 114 such that the downstream end 116 of a first protrusion 110 becomes the beginning of the upstream 118 of an adjacent protrusion 112. The design in Figure 1B does not have a significant valley (i.e., a portion of constant diameter) between adjacent protrusions.

[0013] FIG. 2 shows exemplary first bypass control sleeve 202 and exemplary second bypass control sleeve 204, which mainly have different relative dimensions. Each bypass control sleeve may have a raised portion 206 with discrete protrusions or valleys 208 between the protrusions. The raised portions and valleys extend around the circumference of the sleeve. The raised portions may extend around the circumference in a pattern of repeating discrete circles, or in a spiral or helical pattern, along the length of the sleeve. The valleys and raised portions may be disposed along the entire length of the sleeve, or only along a portion of the sleeve. Valley 208 may have an essentially constant diameter (i.e., varying within 1 mm) along the width of the valley. The width of valley 208 may be within the range of 50% to 200% of the width of raised portion 206.

[0014] Each raised portion 206 includes an upstream side 210 and a downstream side 212. The upstream side includes a front face that may include a steep slope or a concave curve. In one example, the curved portion of the front face of the raised portion may end at a peak while being oriented substantially perpendicular to, or perpendicular to the circumference of, the sleeve. As the liquid flows along the upstream side of raised portion 206, the liquid may be deflected radially outward. The radial liquid deflection may increase turbulence, disrupt, or slow down the supply flow passing through the annular space between the inside of the pressure vessel and the sleeve.

[0015] In the example of FIG. 2, the downstream side of each raised portion is different from the upstream side of the raised portion such that the raised portion is asymmetric, i.e., longer, not as steep, and / or more gently curved. In one example of an asymmetric raised portion, the rear face may curve, for example, in a concave curve, but has an initial slope that is not as steep as the front face and / or a larger radius of curvature. In one example, the rear face may curve continuously. The length, slope, and / or curvature of the downstream side may suppress the formation of vortices. Particularly when the vortices are minimized, the water follows the downstream side of the raised portion. Thereby, the flowing water is drawn downward into the valley. The water flowing through the valley is deflected upward by the upstream side of the raised portion, disrupting the water flow in the annular space between the inside of the pressure vessel and the sleeve.

[0016] The sleeves 202, 204 shown in FIG. 2 include asymmetric ridges 206, with a valley 208 disposed therebetween. The distal (i.e., radially outer) end of the front face 210 of each ridge 206 has a concave curve or a steep positive slope, while the distal end of the rear face 212 also has a concave curve or a negative slope. In this way, the front face 210 and the rear face are generally connected by a sharp peak, transition, or discontinuity in the gradient. The downstream side or rear face 212 of each ridge 206 may have a gentle, substantially linear slope from the peak of the ridge to a curve ending at the abutting valley, or to a continuous concave curve between the peak and the valley. In one example, the ridges along the length of the sleeve may have the same width, and the valleys along the length of the sleeve may have the same width. In other examples, the width of the ridges and / or valleys may vary along the length of the sleeve.

[0017] The space between the top of each peak of the sleeve and the inside of the pressure vessel may be 0.02 - 0.2 cm (0.008 - 0.08 inches).

[0018] The distance between the peaks of adjacent ridges may be about 0.2 cm to about 1.6 cm (0.08 - 0.6 inches).

[0019] The depth of the valley between adjacent ridges may be about 0.02 cm - 0.3 cm (0.008 - 0.12 inches). The depth of the valley is the distance between the height of the peak and the floor of the valley.

[0020] The bypass control sleeve according to this disclosure has an inner diameter that matches the outer diameter of the spiral membrane element. The bypass control sleeve may have a length of 400 mm (16") or less, or 350 mm (14") or less, or 300 mm (12") or less, or 250 mm (10") or less, or 200 mm (8") or less, or 150 mm (6") or less. The bypass control sleeve may have a length of 100 mm (4") or more. In another example, the bypass control sleeve may have a length that substantially extends the entire length of the spiral membrane element. Each spiral membrane element, or a series of elements in a pressure vessel, is preferably secured by at least one bypass control sleeve, for example, on the downstream end of the spiral membrane. Alternatively or additionally, the spiral membrane element or series of elements may be connected to the element. The ment or series of elements may be secured with a bypass sleeve at its upstream end. Two or more bypass control sleeves may be used. For example, one bypass control sleeve may be secured to the upstream end of a membrane element and another to the downstream end of the membrane element. In another example, the bypass control sleeves may be secured to each end, and one or more sleeves may also be positioned along the length of the spiral membrane element. One or more sleeves may extend over part or the entire length of the spiral membrane element. In an example where multiple spiral membranes are connected in series within the same pressurized vessel, the spiral membrane elements may be secured with one or more bypass sleeves before being placed in series within the pressurized vessel.

[0021] Figures 3A and 3B show examples of spiral membrane elements 302 having multiple bypass control sleeves 304. Figure 3A shows the bypass control sleeves attached to the upstream and downstream ends of the spiral membrane. In the example shown, the multiple bypass control sleeves 304 are placed on each end of the spiral membrane element 302. Alternatively, a single bypass control sleeve 304 with the same total length as the multiple sleeves 304 shown may be used. Figure 3B shows a spiral membrane element 302 with a bypass sleeve 304 that extends substantially along its entire length. Alternatively, one of the longer sleeves 304 may be used to cover the entire length of the element.

[0022] During use, a portion of the feed flowing through the annular space flows above the peak of the sleeve, while the remainder of the feed flowing through the annular space contacts the steeply curved upstream side of the raised section and is radially deflected toward the portion of the feed flowing above the peak. This creates turbulence within the annular space, slowing and limiting the flow rate outside the element. Less flow through the element allows more feed to pass through, contributing to increased product recovery. Turbulence can also help refine the annular space, helping to prevent the accumulation of solids or bacterial growth within the space.

[0023] The bypass control sleeves according to this disclosure may be made of plastic or other materials. The bypass control sleeves can be, for example, molded or machined. Examples of suitable materials acceptable for contact with food include thermoplastic polymers such as polypropylene, polyethylene (PE), low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene (EIHMWPE), polyvinylidene fluoride, polytetrafluoroethylene, and thermoplastic polyurethane. Other suitable materials acceptable for contact with food include elastomers, fluoroelastomers, and thermosetting polyurethanes. Heat-shrinkable materials such as Raychem semi-rigid modified polyolefins are another example of suitable materials for bypass control sleeves. Semi-rigid heat-shrinkable materials may be molded to form the bypass control sleeve. Optionally, the bypass control sleeves can be made of materials such as nylon, ABS, polyethersulfone, polyetheretherketone, polyetherimide, or stainless steel. The bypass control sleeves can also be made of low-friction materials such as PE or UHMWPE, materials having a low coefficient of friction with stainless steel or glass fiber. Bypass control sleeves can be made from elastomers (such as ethylene propylene diene methylene rubber (EPDM), silicone rubber, or nitrile butazine rubber) or fluoroelastomers (such as copolymers of at least hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2), terpolymers of at least tetrafluoroethylene (TFE), vinylidene fluoride (VDF or VF2), and hexafluoropropylene (HFP), or copolymers of at least tetrafluoroethylene (TFE) and perfluoromethyl vinyl ether (PMVE)). Fluoroelastomers may have a fluorine content of about 66-70%. Fluoroelastomers may be classified under the FKM designation of ASTM D1418 and ISO 1629 and may be marketed under the name Viton™. Bypass control sleeves made from elastomers or fluoroelastomers may have a high coefficient of friction with stainless steel or glass fiber.A lubricant such as glycerin may be used to assist in inserting a bypass control sleeve made of elastomer or fluoroelastomer. The lubricant can be removed after the bypass control sleeve has been inserted, for example, by washing it away.

[0024] The bypass control sleeve can be heated to expand its inner diameter for installation. The heated bypass control sleeve can then be slid over the end of the spiral membrane element and allowed to cool. Upon cooling, the bypass control sleeve shrinks and fits tightly onto the spiral membrane element. Optionally, when cooled, the bypass control sleeve has an inner diameter smaller than the end of the spiral membrane element. This helps to hold the bypass control sleeve in place on the spiral membrane element and may also compress the spiral membrane element. Alternatively, the bypass control sleeve can be stretched without yielding. In this case, the stretched bypass control sleeve is placed over the element and then released, allowing the bypass control sleeve to elastically shrink back to its original size, thereby fitting snugly onto the element or compressing it. In another alternative embodiment, if the bypass control sleeve is formed from a heat-shrinkable material, it can be placed over the spiral membrane and heated to shrink it. The size of the heat-shrinkable material and the bypass control sleeve are selected so that their shrinkage fits tightly onto the spiral membrane element. Optionally, the bypass control sleeve has an inner diameter smaller than the ends of the spiral membrane element when shrunk. This helps to hold the bypass control sleeve in place on the spiral membrane element and may also compress the spiral membrane element. An example of a heat-shrinkable material that can be used is Raychem semi-rigid modified polyolefin, which has a final elongation of 250%(min) and shrinks at temperatures above 125°C, e.g., about 150°C.

[0025] The bypass control sleeve may compress the element sufficiently to reduce its circumference by approximately 0.2 to 0.4 cm. The bypass control sleeve may compress the element with sufficient force to hold the bypass control sleeve in place, prevent the supply channel from opening, prevent the element from expanding or contracting, or any combination thereof, during typical operating conditions which may include contact with a high-temperature supply flow. For example, the bypass control sleeve may compress the element sufficiently such that the compressive force is greater than the force applied to push the bypass control sleeve downstream, in combination with the underlying coefficient of friction and interference due to the structure of the bypass control sleeve. For example, for a bypass control sleeve with a cross-sectional area of ​​3.5” square and facing a pressure drop of 15 psi, the force applied to push the control sleeve downstream is approximately 52.5 pounds.

[0026] The outer diameter of the bypass control sleeve may initially be slightly larger or smaller than the inner diameter of the pressure housing. If it is slightly larger, or if the bypass control sleeve remains stretched when installed on the spiral membrane element, the outer diameter of the bypass control sleeve can be reduced after the bypass control sleeve is installed, but before or during the insertion of the spiral membrane element into the pressure housing. For example, the bypass control sleeve can be machined or thermally modified (i.e., remodeled) to reduce its diameter. Alternatively, the bypass control sleeve may be compressed within the pressure housing, for example, when the spiral membrane element is placed through the pressure housing itself or in a fixture that slides against the pressure housing. Elements having bypass control sleeves may have the force required to insert them into the housing, slide them within the housing, and / or remove them from the housing, which is less than or equal to the force required for existing caged and / or shelled sanitary elements, such as the Dow Hypershell™ RO8038 or Suez AF8038 sanitary RO modules, for example, at least 10%, at least 20%, or at least 30%.

[0027] Optionally, one or more additional bypass control sleeves can be placed at one or more positions along the length of the spiral membrane element. The bypass control sleeves are relatively rigid and optionally prestressed to help resist expansion or unwinding of the spiral membrane element during filtration or disinfection procedures. However, one bypass control sleeve on the downstream end of the spiral membrane module is expected to be sufficient.

[0028] Table 1 below shows the results of a computational fluid dynamics (CFD) analysis comparing bypass flow rates at a pressure difference of 68.95 kPa (10 psi) for a curved peak design (i.e., asymmetrical design) as shown in Figure 2, specifically the rounded peak design (Figure 1A), the triangular peak design (Figure 1B). The peak-to-wall distance for each design in the analysis was 0.1 cm (0.04 inches). As can be seen in the table, the curved peak design shows improvement (i.e., reduced bypass flow rate) over the two prior art examples. At a pressure difference of 68.95 kPa, the sleeve in Figure 2 showed approximately 20% improvement over the triangular peak shape and approximately 60% improvement over the rounded peak shape.

[0029] [Table 1]

[0030] Figure 4 shows a graph comparing the flow rate in gallons / min as the pressure change increases for the three designs described above, which have a peak-to-wall gap of 0.1016 cm (0.04 inches) (distance from the peak to the inside of the pressure vessel), and an additional curved (asymmetrical) sleeve design with a peak-to-wall gap of 0.05 cm (0.02 inches).

[0031] The reduction in bypass flow resulting from the curved sleeve design can help increase the recovery rate of the filtration process. While not bound by theory, it is assumed that an asymmetrical peak design with a steep front face, such as shown in Figure 2, increases turbulence and thereby reduces bypass flow compared to rounded or triangular peak shapes.

[0032] Figure 5 shows the results of a CFD modeling experiment illustrating the Reynolds number of bypass flow around sleeves with curved (asymmetric), triangular, and rounded ridges having the same flow and peak-to-wall distance. As shown in Figure 5, the flow values ​​for the curved (rounded) sleeve include laminar flow. Although not intended to be limited by theory, the inventors believe that flowing water is drawn into the valleys of the curved (asymmetric) sleeve, thereby reducing the bypass flow.

[0033] Figure 6 is a schematic diagram showing an exemplary test system using a caged spiral RO membrane element with a bypass control sleeve module 610 having either a curved peak design or a triangular peak design in different tests, around the spiral membrane element. Ultrafiltration permeate (UF permeate) 602 from an upstream process, e.g., sweet whey or acid whey process, may be used as feed to the test system and added to a feed tank 604. The UF permeate may then be pumped toward module 610 via a feed pump 606 and a recirculation pump 608. The permeate 612 is discharged from the system, while the concentrate 614 is partially returned to the feed tank 604 and partially recirculated toward module 610 via the recirculation pump 608. The baseline pressure is determined at the outlet of the feed pump. The recirculation pump increases the pressure to control the flow through module 610. The system pressure drop is determined as the pressure difference between the boost pressure and the baseline pressure (i.e., the pressure difference between the inlet and outlet of the recirculation pump 608), which is the same as the pressure difference between the element inlet and the element concentrate outlet. In one example, 75–77% of the concentrate 614 is recirculated to the element, and 23–25% of the concentrate 614 is returned to the feed tank 604. In the exemplary system, a control valve (not shown) is configured to regulate the flow of concentrate between the feed tank return portion and the recirculation portion. In the exemplary system, a heat exchanger may be placed in the path between the recirculated concentrate and the feed tank to control the system temperature to approximately 12–16°C.

[0034] In exemplary tests, the bypass control sleeve with a curved peak according to this disclosure (similar to the second bypass control sleeve 204 in Figure 2) was compared to Dow Flimtec™ Hypershell™ RO8038 having a bypass control sleeve similar to the triangular peak design 104 (triangular peak) in Figure 1B. The triangular peak sleeve around the element had a one-piece sleeve with a length of 38 inches (965.2 mm) and a circumference of 633.5 mm at one end, 634.5 mm in the middle section, and 634.5 mm at the second end. The bypass sleeve setting of the curved peak design had two bypass control sleeve segments with a curved peak profile. The two sleeve segments were placed at both ends of the element. The same type of membrane element was used with both the curved peak bypass sleeve and the triangular peak bypass sleeve. Each curved peak bypass control sleeve segment was 13.5 inches long and had a circumference of 633 mm. The element was 38 inches long, with the bypass control sleeve segments covering 13.5 inches at each end, leaving approximately 11 inches of the central caged portion of the element exposed. The exposed caged element between the sleeves had a circumference of 621 mm. Table 2 shows the additional parameters for each of the triangular peak and curved peak bypass control sleeves used in this test, each housed in an 8-inch diameter housing.

[0035] [Table 2]

[0036] Based on a given flow rate, to achieve an optimized pressure drop through an element, for example, 8–12 psids, the recirculation pump typically needs to consume more energy to increase the feed flow rate to achieve the required pressure drop (the feed includes feed from the feed tank and recirculated concentrate). In an exemplary pure water test comparing the triangular peak and curved peak bypass sleeves described above, a 4.5% reduction in housing flow due to the curved peak design compared to the triangular peak resulted in an average 4.4% power reduction of the recirculation pump. Figure 7 shows graphs illustrating the feed flow at a given pressure drop for each of the triangular peak and curved peak design settings described above. As shown in the graphs, the feed flow through the housing with the curved peak design is less at a given pressure drop compared to the triangular peak at the same pressure drop. Table 3 shows the reduction in flow rate in the system with the curved peak bypass sleeve compared to the system with the triangular peak, and the corresponding reduction in recirculation pump power for a given pressure drop.

[0037] [Table 3]

[0038] The results above compare a curved peak bypass control sleeve with a circumference of 633 mm with a triangular peak control sleeve with a circumference of 633.5 mm to 634.5 mm, as previously shown. CFD modeling was performed to determine the flow rate using the curved peak bypass sleeve with a circumference of 630.07 mm to 634.86 mm. The CFD model assumes an 8-inch long bypass control sleeve in a housing with an 8-inch inner diameter. All other parameters of the bypass control sleeve were fixed so that only the peak-to-wall gap changed between tests. The results of the CFD model shown in Table 4 below demonstrate the effect of increasing the peak-to-wall gap of the triangular peak sleeve used in the above tests to approximately the same peak-to-wall gap. Based on the reduced flow rate seen in Table 4, a greater response to energy performance is expected if the curved peak bypass control sleeve setting includes a peak-to-wall distance that is the same as or close to the peak-to-wall distance of the triangular peak sleeve.

[0039] [Table 4]

[0040] In another exemplary test, 140 gallons of UF permeate were added to the system instead of pure water. A 140-gallon feed tank could be used, but in a specific example, a feed tank capacity of less than 140 gallons was used, and the UF permeate was added in increments of 1 gpm. As 1 gpm of RO permeate exited the system from the element, 1 gpm of feed was added to the feed tank until a total of 140 gallons of feed had been introduced into the system, at which point no more fresh feed was added to the feed tank. The concentrate from the element was returned to the feed tank and recirculated until the UF permeate was concentrated to approximately 4% Brix to a maximum of approximately 20% Brix, for example, approximately 4.5% Brix to approximately 18.5% Brix, at which point the test was terminated. During the batching of 140 gallons of UF permeate, the two element settings being compared were run at 10 psid throughout the entire test period, and the feed pressure was adjusted to maintain the set permeate flow rate. Both processes were run for approximately 130 minutes, and the feed (UF permeate) was concentrated to approximately 4% Brix to 18.5% Brix. In cases where the feed contained lactose, the starting material had approximately 4.5% lactose, which was then concentrated to a maximum of approximately 20% lactose by the end of the trial.

[0041] Figure 8 is a graph of the housing flow in gpm per gallon of generated RO permeate at 10 psid between the inlet and outlet of the recirculation pump 608 for both the triangular peak sleeve and the curved peak sleeve. The housing flow was measured between the recirculation pump and the element inlet. As the RO permeate increases, the UF permeate feed becomes more concentrated as the concentrate returns to the feed tank and is recirculated. As seen in Figure 8, the curved peak bypass sleeve maintained a lower flow rate compared to the triangular peak sleeve as the RO permeate increased up to approximately 100 gallons, at which point the flow rates of both systems converged to approximately the same. The results indicate that the curved peak design provides a significant improvement over the triangular peak design during the initial stages of UF permeate treatment, particularly when the UF permeate concentration is in the 4.5%–15% Brix range. For example, the curved peak design shell reduced the required housing flow by 6% and the corresponding power by 8.4% compared to the triangular peak sleeve. For example, when the concentration increased to 15%–20% Brix, the two systems yielded similar results, although the curved peak still provided slightly improved results, with the required housing flow reduced by ≤0.5% and the corresponding power reduced by ≤1.7% compared to the triangular peak sleeve. The triangular peak sleeve can be more dependent on the viscosity of the feed compared to the bypass shell of the curved peak design.

[0042] Figure 9 provides graphs of the recirculation pump output in kW against the Brix of the feed solution when the feed solution is concentrated, for each of the triangular peak sleeve and curved peak design bypass shells described above. Below 14.5% Brix, the graphs show a significant improvement in flow rate (and consequently power consumption) using the curved peak design bypass shell compared to the triangular peak sleeve. Above 14.5% Brix, the improvement is less significant, but still slightly better than the triangular peak design.

[0043] This specification uses examples to disclose the present invention in best mode and to enable those skilled in the art to carry out the invention, including the fabrication and use of any apparatus or system and the execution of any incorporated method. The patentable scope of the present invention is defined by the claims and may include other embodiments that those skilled in the art may conceive.

Claims

1. A bypass control sleeve for a spiral film element, wherein the bypass control sleeve is a. Asymmetrical projection, or b. A projection having a concave, curved front surface, Having one or more of the following, The protrusion is a bypass control sleeve that wraps around the bypass control sleeve in a circular direction.

2. The bypass control sleeve according to claim 1, wherein the projections are wound around the bypass control sleeve in a circumferential direction in a discrete circular, helical, or spiral pattern.

3. The bypass control sleeve according to claim 1 or 2, wherein each projection has a valley between them, and the width of each valley is 50 to 200% of the width of the projection.

4. The bypass control sleeve according to claim 3, wherein each of the valleys has a constant diameter over its width.

5. The bypass control sleeve according to any one of claims 1 to 4, wherein the projection has a front surface with a concave curve on the upstream side and a rear surface with a concave curve on the downstream side.

6. A bypass control sleeve according to any one of claims 1 to 4, having an asymmetrical projection.

7. The bypass control sleeve according to any one of claims 1 to 6, wherein the front surface of the projection is configured to radially deflect the supply flow in a direction perpendicular to the circumference of the sleeve.

8. The bypass control sleeve according to any one of claims 1 to 7, wherein adjacent protrusions have a peak-to-peak distance of 0.2 cm to 1.6 cm.

9. The bypass control sleeve according to claim 3 or 4, wherein the valley portion has a depth of 0.02 cm to 0.3 cm.

10. A combination comprising a bypass control sleeve according to any one of claims 1 to 9, which is fixed on a membrane element and installed inside a pressurized vessel.

11. The combination according to claim 10, wherein a space of 0.02 cm to 0.2 cm is provided between the peak of the projection of the bypass control sleeve and the inner wall of the pressurized vessel.

12. The combination according to claim 10 or 11, wherein a space of 0.0254 cm to 0.0762 cm is provided between the peak of the projection of the bypass control sleeve and the inner wall of the pressurized vessel.

13. A method for installing a bypass control sleeve according to any one of claims 1 to 9, comprising sliding the sleeve on the end of a spiral membrane element.

14. The method according to claim 13, further comprising heating a bypass control sleeve before sliding the sleeve over the end of a spiral membrane element.

15. The method according to claim 13, comprising extending a bypass control sleeve while sliding the sleeve over the end of a spiral membrane element, and releasing the sleeve after sliding over the end of the element to elastically contract it.

16. The method according to claim 13, wherein the bypass control sleeve comprises a heat-shrinkable material, and the method further comprises sliding the sleeve over the end of a spiral membrane element and then heating the sleeve.

17. The method according to any one of claims 13 to 16, wherein sliding a sleeve on the end of a spiral membrane element comprises sliding a sleeve in the longitudinal direction of the spiral membrane element.

18. A method for manufacturing a bypass control sleeve, comprising forming projections on the outer surface of the sleeve, wherein each projection has a front surface including a concave curve and / or the projections are asymmetrical.

19. The method according to claim 18, wherein the bypass control sleeve is molded before being fixed to the spiral membrane element.

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