System and method for improved flow distribution in ultrafiltration arrays

Abstract

The present invention provides batch or semi-batch methods and systems for processing a supply solution. The superfiltration system is suitable for switching between two modes: a recirculation process in which the retaining fluid flow from the superfiltration membrane elements is reused, and a flushing process in which the retaining fluid flow is moved to the outlet. The superfiltration system includes an array design optimized to enhance flashing efficiency during the flashing process by equalizing the hydraulic residence times of different flow paths through the pressure vessel array. Substantially equal hydraulic residence times result in more uniform movement of solute from the system, a reduction in the overall flash volume for moving accumulated solute, and minimization of variations in the year-to-year distribution of solute accumulating within the system.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to U.S. Provisional Patent Application No. 63 / 497,700, filed April 21, 2023, under 365(c) of the U.S. Patent Act, which is incorporated herein by reference in its entirety.

[0002] The present invention relates to systems and methods for filtering feed solutions in batch and semi-batch manner using superfiltration. More specifically, the present invention provides a superfiltration system comprising an array of filter vessels in a recirculation loop configured to result in a more efficient flushing cycle. [Background technology]

[0003] To provide a more detailed description of the current state of the art to which this invention belongs, several patents, patent applications, and publications are referenced herein. The entire disclosures of each of these patents, patent applications, and publications are incorporated herein by reference.

[0004] The combination of climate change and water scarcity is increasing the need to purify alternative water sources for beneficial use with lower energy consumption. Currently, conventional ultrafiltration is widely used to meet this need. Conventional ultrafiltration is a pseudo-steady-state ultrafiltration membrane process in which a pressurized feed flow is continuously split into two flows: a permeate flow with low solute concentration and a retained liquid flow with high solute concentration. The system's recovery rate is generally defined as the ratio of the permeate flow rate to the feed flow rate. Further recovery of the feed flow is achieved by adding additional ultrafiltration membrane elements in series. As a result, conventional ultrafiltration systems operate over a very narrow range of recovery rates for any given design. The physical engineering design of a conventional ultrafiltration system can also affect the overall recovery, water quality, and flux of the system. Further research has revealed that the recovery of individual membrane element pressure vessels and consequently ultrafiltration membrane elements can be adversely affected by the physical design of the ultrafiltration system (Verhuelsdonk et al., “Modeling the impact of using multi-port RO pressure vessels in seawater reverse osmosis desalination plants using special simulation software” Desalination and Water Treatment 5 (2009) 192-197 (www.deswater.com)). Verhuelsdonk examined a conventional ultrafiltration system used in seawater treatment and identified that poor flow distribution within the membrane pressure vessel array can adversely affect the recovery of elements in different pressure vessels. This can lead to different contamination and scale formation in conventional ultrafiltration systems, complicating the problems associated with them.

[0005] Ultrafiltration systems were developed specifically to address the spatial limitations on recovery within conventional, stationary, steady-state ultrafiltration systems. Batch and semi-batch ultrafiltration are recently developed methods for desalination of aqueous solutions using ultrafiltration that utilize two distinct main operating modes. In the first mode, a solute-rich retaining liquid stream is recycled and mixed with the supplying liquid before entering a pressure vessel containing a membrane. As a result, the concentration of solute in the retaining liquid increases over the duration of the first operating mode. In the second mode, the retaining liquid is directed to waste, allowing for the deconcentration of accumulated solute from within the system. The pressure of the solution supplied to the ultrafiltration membrane elements is adjusted to provide the desired production of a permeate containing a low solute concentration. These batch and semi-batch ultrafiltration systems offer many advantages, including lower energy consumption and the ability to operate over a wide range of different recovery rates by decoupleing the system design from the target recovery rate. [Overview of the project] [Problems that the invention aims to solve]

[0006] The operational experience of the system described by Efraty (see, for example, U.S. Patents Nos. 7,695,614, 7,628,921, and 8,025,804) has demonstrated that the presence of solute retention in the system at the end of a second operating mode cycle can significantly reduce some of the advantages of semi-batch ultrafiltration. For example, deposited solute can increase the supply pressure required to support permeation, resulting in increased energy savings. Deposited solute typically also decomposes the treated solution stream. If the solute consists of sparingly soluble salts, the risk of scale formation increases due to the "aging" of salts retained in the system. In scale-forming applications, extending to a second operating mode is often beneficial in reducing solute retention rates. However, there is clearly still a need for batch ultrafiltration systems that minimize salt retention in the system and allow for improved operation of semi-batch systems. [Means for solving the problem]

[0007] Accordingly, this specification provides a semi-batch / batch ultrafiltration system for processing or purifying solute-containing solutions.

[0008] In a first aspect of the present invention, the system is The source of the fluid to be processed, A recirculation loop for processing fluids, A pressure vessel array having an array inlet for the feed, an array outlet for the retaining fluid, and a permeate discharge line, Recirculation means suitable for increasing the fluid pressure between the array outlet and the array inlet, A recirculation loop including, A valve assembly suitable for restricting flow within the recirculation loop, suitable for enabling discontinuous discharge of concentrated fluid from the recirculation loop to the waste outlet, and may be suitable for restricting flow from the recirculation loop to the waste outlet, wherein at least one component of the valve assembly is located within the recirculation loop, and the valve assembly is A high-pressure pump suitable for introducing pressurized fluid from a fluid source into a recirculation loop, A control device suitable for operating the valve assembly and Includes, The pressure vessel array includes a pressure vessel stack assembly, and the pressure vessel stack assembly is A plurality of parallel pressure vessels, including a first pressure vessel, a last pressure vessel, and at least one pressure vessel positioned between the first pressure vessel and the last pressure vessel, Each of the pressure vessels includes one or more inlet ports located closest to the first end of the pressure vessel, one or more outlet ports located closest to the second end of the pressure vessel, and a permeate port located at one of the ends of the pressure vessel. Multiple parallel pressure vessels, wherein the inlet ports of adjacent pressure vessels are connected at the first end, and the outlet ports of adjacent pressure vessels are connected at the second end, An inlet conduit for fluid connection of a stack inlet to the inlet ports of the plurality of parallel pressure vessels, wherein the stack inlet is located closest to the inlet port of the first pressure vessel, An outlet conduit for fluid connection between a stack outlet and the outlet ports of the plurality of parallel pressure vessels, wherein the stack outlet is located closest to the outlet port of the last pressure vessel, and The system includes a configuration in which each individual pressure vessel provides its own unique flow path within the recirculation loop, passing sequentially through the array inlet, stack inlet, individual pressure vessel, stack outlet, and array outlet.

[0009] Furthermore, a method is provided for operating batch or semi-batch ultrafiltration using the system described above, wherein the system alternately switches between a first operating mode and a second operating mode, and a feed solution is used to transfer the solute from the system.

[0010] The novel advantages and features that characterize the present invention are described in detail in the claims, which are attached to and form part of this specification. However, for a better understanding of the present invention, its advantages and the purposes achieved by its use, please refer to the drawings, which form further parts of this specification, and the attached descriptions which illustrate and describe one or more preferred embodiments of the present invention. [Brief explanation of the drawing]

[0011] [Figure 1] A cross-section of a single porous pressure vessel from prior art is shown, along with the superfiltration membrane element housed therein. [Figure 2] A preferred embodiment of the pressure vessel stack assembly described herein is shown in cross-section, showing a plurality of parallel pressure vessels connected to each other using side ports, and also showing a preferred arrangement of inlet and outlet headers. [Figure 3]An alternative embodiment of the pressure vessel stack assembly described herein is shown, showing a plurality of end port vessels connected to an inlet distribution pipe and an outlet distribution pipe, respectively. The distribution pipes are connected to each inlet and outlet header, showing a suitable arrangement. [Figure 4a] An isometric view of a preferred embodiment of the pressure vessel array described herein is shown. [Figure 4b] An isometric view of a preferred embodiment of the pressure vessel array described herein is shown, where the recirculation loop includes a pressure vessel array having a split header. [Figure 5a] A schematic diagram of a batch ultrafiltration system operating in the first mode is shown. [Figure 5b] A schematic diagram of a batch ultrafiltration system operating in the second mode is shown. [Figure 6a] A cross-section of a prior art pressure vessel stack assembly is shown, where the individual flow paths are drawn as dashed lines. [Figure 6b] A cross-section of the preferred pressure vessel stack assembly described herein is shown, where the individual flow paths are drawn as dashed lines. [Figure 7a] A graph showing the solute concentration in the waste stream over time during the second operating mode of a processing system including a prior art ultrafiltration array. [Figure 7b] A graph focused on the transition region of Figure 7a, showing the solute concentration over time for the combined flow resulting from paths through different individual pressure vessels. [Figure 8a] A graph showing the solute concentration in the waste stream over time during the second operating mode of a processing system including a preferred embodiment of the ultrafiltration array described herein. [Figure 8b] A graph focused on the transition region of Figure 8a, showing the solute concentration over time for the combined flow resulting from paths through different individual pressure vessels.

Best Mode for Carrying Out the Invention

[0012] Provided herein are batch or semi-batch ultrafiltration systems and methods for operating such systems. The systems described herein result in improved system flushing and, compared to other configurations of batch and semi-batch ultrafiltration, such as those described in U.S. Patent No. 7,695,614, No. 7,628,921 and No. 8,025,804, result in improved solute removal from the system, reduced solute buildup in the system, reduced operating pressure and energy consumption, and a reduced risk of scale formation when concentrating sparingly soluble salts.

[0013] Here, the same reference numbers throughout the figures refer to drawings showing corresponding structures, and in particular to Figure 1, which shows a prior art pressure vessel 20. The pressure vessel 20 is a multi-port vessel including at least one inlet port 24 located closest to the first end 25 of the pressure vessel 20 and at least one outlet port 26 located closest to the second end 27 of the pressure vessel. In the embodiment of Figure 1, the two inlet ports 24 and the two outlet ports 26 are all shown located on the sides of the vessel (side ports). This configuration facilitates the connection of vessels in parallel (Figure 2). In some cases, as will be described in detail below with respect to Figures 6a and 6b, for example, the first or last vessel in an array of connected vessels does not require two ports at each end of the vessel. In other vessel configurations (see, for example, Figure 3), the inlet ports 24 and outlet ports 26 are located at the first end 25 and the second end 27 of the pressure vessel 20, respectively. A permeate port 28 is located at at least one end of the pressure vessel 20. Figure 1 shows a pressure vessel 20 having permeate ports 28 at both a first end 25 and a second end 27. Undesirable side ports may be omitted from the pressure vessel 20, or they may be fitted with caps 29 as shown in Figure 2.

[0014] The pressure vessel 20 includes one or more superfiltration membrane elements 48 (for example, as described in U.S. Patent No. 5,538,642) axially oriented in parallel with the pressure vessel 20. The superfiltration membrane elements 48 include a membrane that preferentially allows the solvent to pass from the feed concentrate side of the membrane to the permeate side, typically blocking most of the solute in the feed concentrate, and forming a retaining solution on the feed concentrate side of the membrane. The solvent passing through the membrane (generally called permeate) is collected in membrane element permeate tubes 84. The permeate tubes 84 are shown connected to permeate interconnectors 82, each having a sealing mechanism (not shown). The permeate typically flows through the permeate tubes 84 and permeate interconnectors 82 and is extracted from the pressure vessel 20 through a permeate port 28. The axis along which the membrane is oriented preferably coincides with the permeate tubes 84. For clarity, various sealing means between interconnections (e.g., permeate tube 84, permeate interconnector 82, permeate adapter 80) are omitted from the drawings and description. These sealing means between components typically include O-rings. Chevron sealing rings, U-couplings, and other similar form factors are also suitable. In some cases, the sealing means may be partially installed within a retaining groove. The sealing means are preferably partially compressed between the two components they connect to prevent flow through the connection between the components. The sealing means are typically made of elastomer material, but harder plastics are used (e.g., as described in International Publication No. 2011 / 041004). In some cases, interlocking end caps, such as those described in U.S. Patent No. 6,632,356, are used between adjacent membrane elements.

[0015] Here, as shown in Figures 2 and 3, multiple pressure vessels 20 can be assembled to form a pressure vessel stack assembly 18 in either a vertical or horizontal alignment. The pressure vessel stack assembly 18 includes multiple parallel pressure vessels 20. In a preferred embodiment, the pressure vessel stack assembly 18 includes at least three parallel pressure vessels 20 such that there is a first pressure vessel 50, a last pressure vessel 52, and at least one pressure vessel 20 positioned between the first pressure vessel 50 and the last pressure vessel 52. Pressure vessels can be considered “parallel” based on their corresponding connections, similar to how resistors in an electrical circuit are understood to be in parallel. The inlet ports 24 of different parallel pressure vessels 20 are connected by an inlet conduit 100 common to all pressure vessels 20 in a single stack assembly 18. Similarly, the outlet ports 26 of different parallel pressure vessels 20 are connected by an outlet conduit 110 common to all pressure vessels 20 in a single stack assembly 18. A “parallel” vessel is not defined by its relative orientation in space, however, it is preferable that the pressure vessel 20 is also arranged so as to be essentially geometrically parallel in space. As used herein in relation to pressure vessels, the term “essentially geometrically parallel” means that the angle between the cylindrical axes or the angle between the central axes of the pressure vessel is 10 o This refers to pressure vessels that are aligned so that they are less than [a certain value].

[0016] Figure 2 shows how adjacent pressure vessels 20 are connected using adjacent inlet ports 24 and adjacent outlet ports 26. These connections are preferably made using Victaric type connections, but flange connections, threaded connections, and welded connections are all possible means of connecting vessels in parallel. Additional pressure vessels 20 can be installed in parallel using a similar configuration. The two parallel pressure vessels 20 furthest from each other in the pressure vessel stack assembly 18 are referred to as the first pressure vessel 50 and the last pressure vessel 52. The inlet ports 24 of adjacent pressure vessels 20 are connected by inlet conduits 100 near their first ends 25, and the outlet ports 26 of adjacent pressure vessels 20 are connected by outlet conduits 110 at their second ends 27. The inlet conduits 100 fluidly connect the stack inlet 22 to the inlet ports 24 of the parallel pressure vessels 20, and the stack inlet 22 is positioned as close as possible to the inlet port 24 of the first pressure vessel 50 so that all flow into the stack passes through the stack inlet 22. Similarly, the outlet conduit 110 fluidly connects the stack outlet 30 and outlet port 26 of the parallel-installed pressure vessels 20. The stack outlet 30 is positioned closest to the outlet port 26 of the last pressure vessel 52 so that the total retained fluid flow leaving the stack passes through the stack outlet 30.

[0017] In this configuration, the number of pressure vessels 20 in each pressure vessel stack assembly 18 is preferably more than 2 and less than 8. Higher values ​​are based on the progression of pressure drops through the inlet port 24 and outlet port 26 in the flow. Ideally, to provide a more uniform flow in each pressure vessel 20, the pressure drop in the superfiltration element is greater than the pressure drop at the ports. More preferably, the ratio of the pressure drop in the pressure vessels (from the inlet port 24 to the outlet port 26) to the maximum pressure difference at the same end (either the first end 25 or the second end 27) between the two parallel pressure vessels is greater than 5:1, more preferably 10:1, and even more preferably 15:1.

[0018] In other words, the pressure vessel array 16 has a first pressure drop between the inlet port 24 and the outlet port 26 of one pressure vessel 20, and the pressure vessel array 16 also has a second pressure drop which is the maximum pressure difference between either the first ends 25 of both of the two parallel pressure vessels 20 or the second ends 27 of both, and the ratio of the first pressure drop to the second pressure drop is greater than 5:1, more preferably greater than 10:1, and more preferably greater than 15:1.

[0019] The inlet conduit 100 and outlet conduit 110 can take different forms in different systems. However, each inlet conduit 100 includes a flow path for distributing a common processing solution (also referred to herein as “feed”) to a plurality of parallel containers through an inlet port 24. Similarly, each outlet conduit 110 includes a flow path for collecting and converging the retaining fluid flows from the outlet ports 26 of the plurality of parallel containers 20. In the embodiment shown in Figure 2, the containers 20 have side ports, and the inlet conduit 100 includes both a gap region 101 located within each adjacent container 20 (upstream of all elements in the container) and an open region 103 for the flow in the inlet port 24 connecting these adjacent containers 20. Similarly, the outlet conduit 110 in Figure 2 includes both a gap region 111 located within each adjacent container 20 (downstream of all elements in the container) and an open region 113 for the flow in the outlet port 26 connecting these adjacent containers 20.

[0020] Figure 3 shows an alternative embodiment using an end-port superfiltration vessel 20 which similarly yields a pressure vessel stack assembly 18. In this embodiment, the inlet conduit 100 is a manifold suitable for distributing a common supply solution to the inlet ports 24 of multiple parallel pressure vessels 20. Similarly, the outlet conduit 110 is a manifold connecting the outlet ports 26 from different parallel pressure vessels 20 to a common retaining fluid flow. Similar to the embodiment in Figure 2, the inlet header 60 is connected to the stack inlet 22 which is connected to the inlet conduit 100. Similarly, the outlet header 62 is connected to the stack outlet 30 which is connected to the outlet conduit 110.

[0021] The filtration system preferably includes a plurality of pressure vessel stack assemblies 18, including a first pressure vessel stack assembly 70 and a last pressure vessel stack assembly 72, as shown in Figures 4a and 4b. On the other hand, Figures 2 and 3 show individual pressure vessel stack assemblies 18, and Figure 4a shows an assembly of a plurality of pressure vessel stack assemblies 18 arranged in parallel to form a pressure vessel array 16. Each pressure vessel stack assembly 72, including the first pressure vessel stack assembly 70 and the last pressure vessel stack assembly 18, is connected to one another in parallel. The stack inlet 22 of each pressure vessel stack assembly 18 is connected to an inlet header 60, and each inlet header 60 has an inlet 64 located closest to the first pressure vessel stack assembly 70. The stack outlet 30 of each pressure vessel stack assembly 18 is similarly connected to an outlet header 62, and each outlet header 62 has an outlet header outlet 66 located closest to the last pressure vessel stack assembly 72. Each of the individual pressure vessels 20 may include a separate flow path 76 (see Figures 6a and 6b) within a recirculation loop 32 (Figures 5a and 5b) that passes sequentially through the array inlet 86, inlet header 60, stack inlet 22, individual pressure vessel 20, stack outlet 30, outlet header 62, and array outlet 88. The portion of the pressure vessel array 16 between the array inlet 86 and the array outlet 88 (e.g., the inlet header 60, stack inlet 22, individual pressure vessel 20, stack outlet 30, and outlet header 62) is shown in Figures 4a and 4b, but not in Figures 5a and 5b. The array inlet 86 is defined as the location directly upstream of the branching point of one separate flow path 76, and the array outlet 88 is defined as the location directly downstream of the confluence point of all separate flow paths 76.

[0022] Continuing to refer to Figures 4a and 4b, the inlet header 60 connected to the pressure vessel stack assembly 18 delivers the supply solution to the stack inlet 22 located closest to the inlet port 24 of the first pressure vessel 50. In this configuration, the solution entering the stack inlet 22 is fluidly connected to each of the parallel pressure vessels 20 via their inlet ports 24. The stack outlet 30 located closest to the outlet port 26 of the last pressure vessel 52 is connected to the outlet header 62. In the case of the pressure vessel array 16 configured in a substantially rectangular box shape as shown in Figures 4a and 4b, the stack outlet 30 is located at the corner opposite to the corner of the stack inlet 22, most preferably at the diagonally opposite corner in the x, y, and z directions. In this configuration, the solution exiting the stack outlet 30 is fluidly connected to each of the parallel pressure vessels 20 in the stack via the outlet port 26. In addition, the stack inlet 22 is in fluid communication with the stack outlet 30 through multiple separate flow paths through each pressure vessel 20, passing through feed concentrate channels of the superfiltration membrane elements 48 (not all superfiltration membrane elements are shown for clarity). Figures 2 and 3 show four pressure vessels 20 in each pressure vessel stack assembly 18, but the preferred number of pressure vessels 20 in a pressure vessel stack assembly 18, which is part of a pressure vessel array 16, is more than two and less than ten. Preferably, each pressure vessel 20 may house 3 to 8 elements 48 in series.

[0023] Figure 4a shows one embodiment having multiple pressure vessel stack assemblies 18 arranged in parallel to form a pressure vessel array 16. The solution is transported from the array inlet 86 to the inlet header inlet 64 and inlet header 60. (The inlet header inlet 64 is upstream of all the pressure vessel stack assemblies 18 and is closest to the first pressure vessel stack assembly 70.) The solution is distributed from the inlet header 60 to the stack inlets 22 of the multiple pressure vessel stack assemblies 18. From the stack inlets 22, the solution passes through at least a portion of the inlet conduit 100 and then through one of the pressure vessels 20. At the downstream end 27 of the pressure vessel, the solutions from different vessels 20 merge in the outlet conduit 110 and then enter the outlet header 62. The solution in the outlet header 62 exits through the outlet header outlet 66. (The outlet header outlet 66 is downstream of each pressure vessel stack assembly 18 and is closest to the last pressure vessel stack assembly 72.) The solution that exits the pressure vessel array 16 and passes through the outlet header outlet 66 is transported to the array outlet 88. In this configuration, the solution entering the pressure vessel array 16 at the array inlet 86 is in fluid communication with the array outlet 88, and multiple flow paths between the array inlet 86 and the array outlet 88 pass through each of the pressure vessel stack assemblies 18, through the individual pressure vessels 20, and through the feed concentrate channels 84 of the superfiltration membrane element 48 (shown in Figures 1 and 2). Based on the system's hydraulic pressure and flow path length, the number of parallel pressure vessel stack assemblies 18 in each pressure vessel array 16 is preferably more than 2 and preferably less than 30. For pressure vessel arrays 16 larger than this, many advantages are expected to be lost.

[0024] Referring here to Figure 4b, the recirculation loop 32 (shown in Figures 5a and 5b) includes two or more pressure vessel stack assembly sets 19, each set connected in parallel to a common array inlet 86 and a common array outlet 88. Each pressure vessel stack assembly set 19 includes an inlet header 60 connected to the array inlet 86 and an outlet header 62 connected to the array outlet 88. The pressure vessel stack assembly set includes a first pressure vessel stack assembly 70, a last pressure vessel stack assembly 72, and at least one additional pressure vessel stack assembly 18 between them. Meanwhile, each pressure vessel stack assembly 18 in set 19 includes a stack inlet 22 connected to the inlet header 60 at a first end 25 and a stack outlet 30 connected to the outlet header 62 at a second end 27. (Since both “first end 25” and “second end 27” describe orientation with respect to the pressure vessel axis, the descriptive terms apply equally to the pressure vessel 20 (as shown in Figures 1, 2, and 3), the pressure vessel stack assembly 18, and the pressure vessel stack assembly set 19, respectively.) The header inlet 64 is located between the inlet header 60 and the array inlet 86, and the header inlet 64 is closest to the first pressure vessel stack assembly 70. The header outlet 66 is located between the outlet header 62 and the array outlet 88, and the header outlet 66 is closest to the last pressure vessel stack assembly 72.

[0025] The pressure vessel stack assembly set 19 provides several separate flow paths 76 (as shown, for example, in Figures 6a and 6b). Referring to Figure 4b, each pressure vessel 20 in two pressure vessel stack assembly sets (19, 19', etc.) is thought to provide one separate flow path 76 in the recirculation loop 32, passing through the array inlet 86, the pressure vessel stack assembly set 19, and the array outlet 88 in sequence.

[0026] Continuing to refer to Figure 4b, each pressure vessel assembly set 19 includes an inlet header 60, an outlet header 62, a header inlet 64, and a header outlet 66. The first and second pressure vessel assembly sets (19, 19') include several corresponding parts, including the first and second inlet headers (60, 60'), outlet headers (62, 62'), header inlets (64, 64'), header outlets (66, 66'), the first pressure vessel stack assembly (70, 70'), and the last pressure vessel stack assembly (72, 72'). Some of these parts are illustrated in Figure 4b and numbered relative to the first pressure vessel assembly set 19. Figure 4b also shows labels for some of the main parts of the second pressure vessel assembly set 19'.

[0027] Figure 4b further illustrates how outlet headers (62, 62') from two different pressure vessel assembly sets (19, 19') can be collinear, adjacent, and directly connected. The common pipe forming the headers of the two different pressure vessel assembly sets (19, 19') is also considered collinear, adjacent, and directly connected. Similarly, for this purpose, two collinear, adjacent, and directly connected outlet headers (62, 62') are obtained by using a direct connection such as the "T" connection 65 shown in Figure 4b to form a split header, allowing fluid to be removed from the combined header. As shown in Figure 4b, the "T" connection 65 is a preferred embodiment, but any suitable connection that produces a split header can be used. For example, the joints of the pipes forming the split header do not need to be linear, and the diameters of the pipes joined in the split header do not need to be equal. Figure 4b shows the first and second header outlets (66, 66') positioned between the first outlet header 60 and the second outlet header 62'. In some cases, the two header outlets (66, 66') are considered to coincide. As shown in Figure 4b, the arrangement of the inlet header (64, 64') is not visible in this perspective view. However, the structure may be similar, and instead, a split header may be created on the first end 25 by arranging the header inlet (64, 64') between the inlet headers (60, 60'). However, preferably, only one of the combinations of inlet headers and one of the combinations of outlet headers is a split header.

[0028] Figure 5a shows one embodiment of the filtration system described herein. This filtration system 2 includes a supply solution source 4 containing the solution to be processed. The supply source may be a pressurized supply source or a reservoir (e.g., a tank). A supply pipe 6 transports the supply solution from the supply solution source 4 to a high-pressure pump 8. The discharge from the high-pressure pump is transported by a pressurized supply path 10 to a first joint 12, where the supply solution may be mixed and enter a recirculation loop 32. The recirculation loop 32 includes the first joint 12, the entire pressure vessel array 16, a recirculation line 34, a recirculation means 36, a second joint 38, and at least one valve 40' of a valve assembly 40.

[0029] Continuing with Figure 5a, the mixed solution is transported by the mixing supply pipe 14 to the array inlet 86, from where it is distributed to the pressure vessel array 16, which includes one or more pressure vessel stack assemblies 18 of pressure vessels 20 housing the superfiltration membrane elements 48, as shown, for example, in Figures 2, 3, 4a and 4b. Partial separation occurs in the superfiltration membrane elements 48 (shown in Figures 1, 2 and 3), producing a low-solute concentration permeate discharged from the permeate port 28 of the pressure vessel 20, and a high-solute concentration retaining solution discharged from the pressure vessel outlet port 26. As shown in Figures 4a and 4b, the combined permeate obtained from the permeate port 28 is transported to the permeate outlet 89 of the pressure vessel array 16. The combined retaining solution obtained from the outlet port 26 of the pressure vessel 20 is transported to the array outlet 88 of the pressure vessel array 16.

[0030] Figure 5a shows a valve configuration suitable for a recirculation process or mode, where, for example, a valve or valve mechanism 40' allows flow between the array outlet 88 and the array inlet 86 through the recirculation mechanism 36 and the first joint 12. In this process, the retaining fluid from the array outlet 88 is mixed with the supply solution from the high-pressure pump 8 at the first joint 12, and the mixture is transported to the array inlet 86 by the mixing supply pipe 14. In a preferred embodiment, filtration operates for at least 50%, more preferably 75%, and more preferably 90% of the time in this recirculation process. During this recirculation process, permeate fluid having a lower concentration than the supply is removed from the system 2 through the permeate outlet 89 of the pressure vessel array 16, thereby increasing the concentration of the fluid in the recirculation loop 32 over time. The pressure of the high-pressure pump 8 is typically increased during this operating mode to maintain a substantially constant permeate flow while in recirculation mode.

[0031] Figure 5b shows different valve configurations suitable for a flushing process or mode, where the flow between the array outlet 88 and the first joint 12 is blocked by a valve or valve mechanism 40', and the flow of concentrate from the array outlet 88 is directed out of the recirculation loop 32. In the flushing process, fresh supply solution is supplied to the recirculation loop 32, and the concentrated fluid from the array outlet 88 is removed from the filtration system 2 via the retaining liquid piping 44. Preferably, the system operates for less than 50% of the flushing process time, preferably less than 25%, and more preferably less than 10%.

[0032] Figure 5b further illustrates a different valve configuration that creates an alternative flow path from the second joint 38, allowing for the removal of the high-solute concentration solution from the recirculation loop 32. The concentrated fluid is repeatedly and discontinuously discharged from the recirculation loop 32 by passing through the retaining fluid piping 44 and the valve or valve mechanism in the valve assembly 40, and is discharged from the system at the retaining fluid outlet 46.

[0033] Continuing to refer to Figures 5a and 5b, the recirculation means 36 is required to maintain the flow by adding pressure in the recirculation loop 32 before mixing occurs at the first joint 12 in order to offset the hydraulic pressure loss in the recirculation loop 32. This recirculation means 36 is most commonly a centrifugal pump, but may include other types of pumps and energy recovery devices such as positive displacement pumps using pistons, double pistons, rotors, screws, vanes, turbines or progressive cavities, and other means of guiding the fluid flow such as jets, eductors, weight-reducing tanks, pistons or cylinders. If an electric motor is coupled to the recirculation means, the motor may be equipped with a variable frequency drive for adjusting the motor speed and consequently the pressure and flow rate.

[0034] The valve assembly 40 may include several different configurations of valves and valve means, such as flow throttling devices and flow control devices that can direct, control, or block the flow of fluid. When allowing flow in the recirculation loop, the valve assembly 40 also blocks flow from the recirculation loop 32 through the retaining fluid piping 44 to the retaining fluid outlet 46. As shown in Figure 5b, the valve assembly 40 is also suitable for restricting flow in the recirculation loop 32 and allowing discontinuous discharge of concentrated fluid from a second joint 38 in the recirculation loop 32. The fluid can then pass from the second joint 38 through the retaining fluid piping 44 to the retaining fluid outlet 46. At least one component of the valve assembly 40 is located in the recirculation loop 32. The valve assembly 40 may include two separate two-way valves (40', 40'') as shown in Figures 5a and 5b. Alternatively, the valve assembly may include a three-way valve (not shown) at the second joint 38 that directs the flow from the array outlet 88 to either the array inlet 86 or the retaining fluid outlet 46. Suitable valves and valve means useful for this purpose include, but are not limited to, check valves, backflow prevention valves, conventional valve types (such as ball valves, butterfly valves, globe valves, plug valves or orifice or diaphragm valves), Tesla valves, progressive cavity pumps, energy recovery devices, and any other suitable mechanisms that can mitigate, block, or direct the flow into an undesirable flow path.

[0035] The valve assembly 40 further includes a system (not shown) for acting the valves within the assembly. Any system known in the art for this purpose is suitable for use in the system described herein.

[0036] In a preferred embodiment, the valve assembly 40 includes two valves in series, each suitable for restricting the flow between the second joint 38 and the retaining fluid outlet 46. One of these two valves 40''' is preferably a manual throttle valve suitable for flow control, and the other valve 40'' is suitable for rapid operation by a control device.

[0037] Furthermore, a method for performing batch or semi-batch superfiltration (reverse osmosis or nanofiltration) using the system described herein is provided herein. This method involves pressurizing a feed solution and passing it through a pressure vessel array of superfiltration membrane elements. The superfiltration membrane elements separate the feed solution into a first flow of lower concentration (permeate) and a second flow of higher concentration (concentrate or reject). The valve assembly can be configured to allow multiple repeatable operating modes in the batch or semi-batch process. The multiple operating modes include at least the following: 1) A first operating mode in which a second (concentrate) flow is allowed to flow within the recirculation loop and mix with the pressurized supply solution to form a new mixture which is preferably continuously re-transported to the pressure vessel array of the ultrafiltration membrane elements. Due to the removal of permeate from the recirculation loop during this mode, the solute concentration of the mixture within the recirculation loop increases as a function of time. It is preferable to also increase the applied pressure to the mixture over time in order to at least partially counteract the effects of the increased osmotic pressure. In some preferred embodiments, during this mode, the volumetric flow rate of the first flow (permeate) leaving the recirculation loop is kept within 75% or more preferably 90% of its initial value, and 2) A second mode of operation in which a second (concentrate) flow from the pressure vessel array of the superfiltration element is transported directly from the outlet of the pressure vessel array to the waste outlet. In this second mode, the configuration of the pressure vessel array results in a substantially uniform flushing profile of solute concentration in the second flow with respect to time. As used herein, the term “substantially uniform” refers to a concentration-to-time curve in which the time range over which the solute concentration in all individual flow paths 74 within the pressure vessel array 16 or pressure vessel stack assembly 18 reaches 50% of their initial value is less than 10%, less than 7%, less than 5%, less than 3%, less than 2.5%, or less than 2% of the average of these times for each individual flow path 74. For example, referring to Figure 8b, if the scalar concentration is 0.5 (50% of the initial value of 1.0), the average time (solid line) over the combined array is approximately 69.5 seconds. The fastest time to reach this concentration is 68.7 seconds (dashed and dotted lines), and the slowest time is 70.5 seconds (dashed line). The time range is 70.5 to 68.7 = 1.8 seconds, which is 2.59% of the average time of 69.5 seconds.

[0038] The filtration system 2 can be repeatedly switched between a first operating mode or recirculation mode and a second operating mode or flash mode. The term "repeatedly," as used herein, refers to an action occurring two or more times within a defined period, such as a day, preferably two or more times within two hours. The switching time can be determined using various setpoints and measurement variables, such as a target conductivity in the loop, a target concentration of the solute, a target viscosity of the retaining fluid, or a target value of another analytical device. To determine when to switch modes, the characteristics of the fluid in the recirculation loop before or after mixing at the first joint 12 can be monitored. Alternatively, setpoints related to the applied pressure or permeate flow may also be used.

[0039] Preferably, the conductivity in the recirculation loop decreases during the second operating mode. More preferably, the time it takes for the measured conductivity in the recirculation loop to decrease from 80% to 20% of the total conductivity range is less than 15 seconds, less than 12 seconds, less than 10 seconds, less than 7 seconds, less than 6 seconds, or less than 5 seconds.

[0040] As briefly described above, each pressure vessel 20 in the pressure vessel array 16 provides a separate flow path 76 in the recirculation loop 32, passing sequentially through the array inlet 86, the stack inlet 22, the ultrafiltration membrane element 48 within its pressure vessel 20, the stack outlet 30, and the array outlet 88. Figures 6a and 6b show two different configurations of the pressure vessel stack assembly 18 and the portions of the separate flow paths (74, 74', 74'', 76, 76', 76'') between the respective stack inlets 22 and stack outlets 30. (Although not shown in the figures 6a and 6b, the array inlet 86 supplies the inlet header 60 and the outlet header 62 supplies the array outlet 88.) Figure 6a shows a prior art pressure vessel stack assembly, where the stack inlet 22 and stack outlet 30 are located at adjacent corners of the stack assembly 18. In the configuration of Figure 6b, the stack inlet 22 and stack outlet 30 are located at opposing corners of the pressure vessel array 16. Figures 6a and 6b show three separate channels created by the three containers. From these figures and the above description of the channels, it is clear that the separate channels 76 are defined by the corresponding containers 20, but the other parts of the two separate channels 76 may overlap.

[0041] Figure 6a, illustrating a conventional method, shows separate flow paths 76, 76', and 76'' through a pressure vessel array 16 consisting of a single prior art pressure vessel stack assembly 18. The stack inlet 22 and stack outlet 30 are in fluid communication with the same pressure vessel 20. In this case, the length of the separate flow path 76 through the last pressure vessel 52 is significantly longer than the separate flow path 76'' through the first pressure vessel 50. When the flow rates and volumes associated with each separate flow path are calculated, the residence times of these two flow paths differ significantly, with a higher flow rate through the separate flow path 76'' than through the separate flow path 76, and a longer residence time in the separate flow path 76 due to the different volumes associated with each flow path.

[0042] Importantly, more piping is required to create the pressure vessel array shown in Figure 6b, for example, in the inlet header and outlet pipes. Nevertheless, this configuration is more economically and environmentally efficient because it offers many advantages, which will be described in detail below. Specifically, by providing substantially equal volumes to each separate flow path, the system described herein minimizes the volume of solution required to purge the system in a flash cycle.

[0043] The advantages of having separate flow paths (between the array inlet 86 and the array outlet 88) having substantially equal length and volume are demonstrated by comparing the stack assemblies 18 shown in Figures 6a and 6b. However, two-dimensional pressure vessel arrays 16, such as those shown in Figures 4a and 4b, which include multiple pressure vessel stack assemblies 18, offer a similar but greater opportunity for a favorable effect on fluid mixing following the discontinuous discharge of the retained concentrated fluid from the recirculation loop 32. When the array inlet 86 and the array outlet 88 are connected at opposing corners of the multi-dimensional pressure vessel array, the difference in residence times of the separate flow paths is reduced. Similar to the effect shown in Figure 6a, the difference in residence times increases when the array outlet 88 is connected closest to the first pressure vessel stack assembly 70, a typical design used in ultrafiltration systems. In contrast, Figure 4a shows the array outlet 88 connected to an outlet header 62 with an outlet 66 located closest to the last pressure vessel stack assembly 72. Simultaneously, the array inlet 86 connects to an inlet header 60 having an inlet 64 located closest to the first pressure vessel stack assembly 70. In the configuration of Figure 4a, the array inlet 86 and array outlet 88 connect to opposing corners of the pressure vessel array 16, resulting in the advantages shown in Figure 4b being obtained in both directions of the two-dimensional array of vessels.

[0044] One way to quantify the difference in flow distance is to utilize the hydraulic residence time and hydraulic volume of each separate flow path. The hydraulic volume is defined as the flow-weighted volume of each section of the system between the array inlet 86 and the array outlet 88 for each different flow path. (In Figures 6a and 6b, the illustrated portions of the separate flow paths 76 and 74 connect to the stack inlet 24 and the stack outlet 30, respectively.) For a section of a system through which there is only one separate flow path (for example, each sub-section of a pressure vessel 20 containing a superfiltration element 48 has only one separate flow path through which it flows), the hydraulic volume of that section with respect to that separate flow path is equal to the feed concentration volume of the superfiltration element 48. However, for a section of a system with multiple separate flow paths, the contribution of the system volume of the section to the hydraulic capacity of each flow path is as follows:

number

[0045] The total hydraulic volume of the separate channels is equal to the sum of the hydraulic volumes of each section j of the system. The theoretical hydraulic residence time for each separate channel can be calculated by calculating the flow rate through the array using computational fluid dynamics, nodal methods, or other means, and determining the flow rate of each separate channel within each system section using the mass balance.

[0046] The theoretical hydraulic residence time assumes a complete plugged flow throughout the system without mixing, diffusion, axial dispersion, or other influences. With respect to the hydraulic residence time of each flow path, it is beneficial that the flow rates in each container are similar to each other, preferably substantially equal to each other, and preferably the difference between the highest and lowest flow rates is less than 20%, more preferably less than 10%, even more preferably less than 5%, or less than 2%.

[0047] Figure 6a shows a wide variation in the path lengths 76, 76', and 76'', hydraulic volume, and hydraulic residence time of each of the separate paths, and the array design of the present invention shown in Figure 6b (only a single stack assembly is shown) shows an improvement, i.e., a minimized difference in the path lengths 74, 74', and 74'' related to the system described herein. By configuring the stack such that the stack inlet 22 is closest to the first pressure vessel 50 and the stack outlet 30 is closest to the last pressure vessel 52 in the stack, each of the separate paths (74, 74', and 74'') has a similar path length, a similar substantially equal associated hydraulic volume, and a similar substantially equal hydraulic residence time. Preferably, the variation in path length, hydraulic volume, and hydraulic residence time is less than 20%, more preferably less than 10%, even more preferably less than 5%, or less than 2%, respectively, compared to the average path length, hydraulic volume, and hydraulic residence time of all the individual paths 74 between the array inlet 86 and the array outlet 88.

[0048] The advantages of the filtration systems described herein for batch or semi-batch superfiltration become apparent when considering a second operating mode, as illustrated by Figures 7b and 8b. In the second operating mode, it is preferable to flush all pressure vessels as uniformly as possible so that all pressure vessels have the same mass of deposited salt moved out of the system. As shown in Figure 7a, some pressure vessels in the array may be over-flushed with large variations in residence times in each separate flow path, while other vessels remain under-flushed at the same time, and the system still contains a large amount of deposited solute. This mass of deposited solute is retained in the system for subsequent operation in the first operating mode and may contribute to increased risk of scale formation and fouling of the system.

[0049] The following embodiments are provided to illustrate the present invention in more detail. These embodiments, which illustrate specific embodiments and preferred modes currently envisioned for carrying out the present invention, are intended to illustrate the invention and not to limit it. [Examples]

[0050] Example: Half-batch ultrafiltration unit System Configuration Array: A single stack assembly It has five containers (each suitable for holding six elements), Each has a 3'' inlet port and a 2.5'' outlet port. Includes 400 square feet of membrane elements Mode: Second operating mode (flashing) Flow rate: 150gpm Solute concentration in the system at t=0: 1 Solute concentration of flush solution: 0 (For clarity, scalar values ​​were used for concentration.)

[0051] The system was modeled using computer hydraulic calculations, taking into account non-ideal mixing and axial dispersion in the pressure vessel, using both prior art stack assemblies and preferred embodiments of the stack assemblies described herein.

[0052] Figure 7a shows a graph of scalar concentration versus time for each separate channel 74, generated using a prior art configuration such as that shown in Figure 6a, with five parallel pressure vessels 20 connected by inlet ports 24 and outlet ports 26. The graph was generated from a computer model that calculated the hydraulic volume and flow rate of each separate channel 74 and considered mixing and dispersion within the pressure vessels. The line labeled PV-1,1 corresponds to the first pressure vessel 50, and PV-5,1 corresponds to the last pressure vessel 52. At a time equal to 0 seconds, the system enters a second operating mode. Figure 7b shows the region of most interest 60–85 seconds after the start of the second operating mode. Figure 7a shows that 71 seconds are required to reduce the scalar concentration of solute in the separate channel corresponding to the first vessel to <0.01. The scalar concentration in the separate channel of the last pressure vessel decreases to less than 0.01 approximately 83 seconds after the start of the second operating mode.

[0053] The inefficiency of flushing during the second mode of operation is shown by the fact that the first pressure vessel 50 is completely flushed before the last pressure vessel 52 begins to break through. During the time from 71 seconds to 83 seconds, the first pressure vessel 50 is over-flushed. This trend continues for the other pressure vessels 20. The solute concentration curve can also be described by the actual hydraulic retention time (which is different from the theoretically defined hydraulic retention time). The actual hydraulic retention time (HRT actual ) explains the mixing and dispersion associated with non-ideal flow. This is typically defined as the point at which the concentration scalar decreases to 50% of its initial value in a negative step tracer test analysis. In this example, the HRT actual is 62.5 seconds for the separate flow path 74 of the first pressure vessel 50 and 73.2 seconds for the last pressure vessel 52. For the five modeled separate flow paths, the average HRT actual for the system was 68.8 seconds with a standard deviation of 3.8.

[0054] [[ID=eleven]] In contrast, FIG. 8a shows a second graph of the hydraulic residence times resulting from the separate flow paths in a preferred embodiment of the system described herein, such as that shown in FIG. 6b. FIG. 8b shows the region of most interest from 60 seconds to 85 seconds. Unlike the prior art array, the preferred array has separate flow paths 76 that are approximately equal within the system, similar to that shown in FIG. 6b. All five vessels show breakthrough of the conductivity scalar within 2 seconds of each other. In this example, the HRT actual is 68.7 seconds for the separate flow path 74 of the first pressure vessel 50 and 70.3 seconds for the last pressure vessel 52. For the five modeled separate flow paths, the average HRT actual for the system was 69.5 seconds with a standard deviation of 0.82.

[0055] These data demonstrate that flushing of the system of the present invention significantly reduces deviations between the various flow paths, allowing more solute to be moved out of the system. Preferably, the distribution of actual hydraulic residence times for each separate flow path has a standard deviation of less than 5 seconds, more preferably less than 4 seconds, and more preferably less than 3 seconds. The benefits are even greater when this methodology for the system of the present invention is applied to multiple pressure vessel stack assemblies 18, such as those shown in Figures 4a and 4b.

[0056] While some preferred embodiments of the present invention have been described and specifically illustrated above, the present invention is not intended to be limited to such embodiments. Rather, although many features and advantages of the present invention are shown in the foregoing description along with details of its structure and function, this disclosure is illustrative only, and it should be understood that modifications in detail, particularly regarding the shape, size and arrangement of parts, can be made within the principles of the present invention to the maximum extent indicated by the broad general meaning of the terms used to express the appended claims.

Claims

1. A filtration system 2 for processing a feed solution using batch or semi-batch ultrafiltration, Recirculation loop 32, A supply solution source 4 for the supply solution to be processed, and a high-pressure pump 8 suitable for introducing the supply solution from the supply solution source 4 into the recirculation loop 32 at a first joint 12, wherein the recirculation loop 32 for processing the supply solution is A pressure vessel stack assembly 18, a pressure vessel array 16 including an array inlet 86 for feed, an array outlet 88 for retaining fluid and a permeate outlet 89, The first joint 12 and, A recirculation means 36 suitable for increasing the fluid pressure between the array outlet 88 and the array inlet 86, The second joint 38 and A high-pressure pump 8, A valve assembly 40 suitable for restricting the flow within the recirculation loop 32 and enabling discontinuous discharge of retaining fluid from the recirculation loop 32 to the retaining fluid outlet 46 at the second joint 38, wherein at least one component of the valve assembly 40 is located within the recirculation loop 32, and the valve assembly 40 is located within the recirculation loop 32. A control device suitable for operating the valve assembly 40 and Includes, The pressure vessel array 16 includes a pressure vessel stack assembly 18, and the pressure vessel stack assembly 18 is At least three pressure vessels arranged in parallel, comprising a first pressure vessel 50, a last pressure vessel 52, and at least one pressure vessel 20 positioned between the first pressure vessel 50 and the last pressure vessel 52. Includes, Each of the pressure vessels 20 includes one or more superfiltration membrane elements, one or more inlet ports 24 located closest to the first end of the pressure vessel 20, one or more outlet ports 26 located closest to the second end of the pressure vessel 20, a permeate port 28 located at one of the first end 25 or the second end 27 of the pressure vessel 20, and one or more superfiltration membrane elements 48. The inlet ports of the adjacent pressure vessels 20 are connected at the first end 25 by the inlet conduit 100, and the outlet ports 26 of the adjacent pressure vessels 20 are connected at the second end 27 by the outlet conduit 110. The inlet conduit 100 fluidly connects the stack inlet 22 to the inlet ports 24 of the at least three pressure vessels installed in parallel, and the stack inlet 22 is positioned closest to the inlet port 24 of the first pressure vessel 50. The outlet conduit 110 fluidly connects the stack outlet 30 to the outlet ports 26 of the at least three pressure vessels installed in parallel, and the stack outlet 30 is positioned closest to the outlet port 26 of the last pressure vessel 52. Filtration system 2, each of the at least three pressure vessels arranged in parallel provides a separate flow path 76 in the recirculation loop 32, passing sequentially through the array inlet 86, the stack inlet 22, the superfiltration membrane element 48 in one of the at least three pressure vessels arranged in parallel, the stack outlet 30, and the array outlet 88.

2. The pressure vessel array 16 includes a plurality of pressure vessel stack assemblies 18, including at least a first pressure vessel stack assembly 70 and a last pressure vessel stack assembly 72. The first pressure vessel stack assembly 70 and the last pressure vessel stack assembly 72 are connected in parallel. The stack inlets 22 of the first pressure vessel stack assembly 70 and the last pressure vessel stack assembly 72 are connected to the inlet header 60. The stack outlets 30 of the first pressure vessel stack assembly 70 and the last pressure vessel stack assembly 72 are connected to the outlet header 62. The inlet header 60 has an inlet 64 located closest to the first pressure vessel stack assembly 70, and The outlet header 62 has an outlet 66 located closest to the last pressure vessel stack assembly 72, The filtration system according to claim 1, wherein each of the pressure vessels 20 provides a separate flow path 76 in the recirculation loop 32, passing sequentially through the array inlet 86, the inlet header 60, the stack inlet 22, the pressure vessel 20, the stack outlet 30, the outlet header 62, and the array outlet 88.

3. Each of the aforementioned separate flow paths 76 has a hydraulic volume, and The filtration system according to claim 1 or 2, wherein the respective hydraulic volumes of the separate flow paths 76 are substantially equal.

4. The filtration system according to any one of claims 1 to 3, wherein the valve assembly 40 includes two valves in series, each suitable for restricting the flow between the second joint 38 and the retaining fluid outlet 46.

5. The filtration system according to any one of claims 1 to 4, wherein one of the valves is a manual throttle valve suitable for flow rate control, and one of the valves is suitable for rapid operation by the control device.

6. The filtration system according to any one of claims 1 to 5, wherein the number of pressure vessels 20 in each pressure vessel stack assembly 18 is greater than two and less than eight.

7. The filtration system according to any one of claims 1 to 6, wherein the number of parallel pressure vessel stack assemblies 18 in each array 16 is greater than 2 and less than 30.

8. A method for performing batch or semi-batch ultrafiltration using the filtration system described in claim 1, The process includes pressurizing the supply solution and transporting the supply solution to the superfiltration membrane element, The superfiltration membrane element separates the supply solution into a first flow and a second flow, the first flow having a lower solute concentration than the supply solution, and the second flow having a higher solute concentration than the supply solution. The filtration system can be configured to enable multiple operating modes, and these multiple modes are A first operating mode, The flow of the second flow is made possible within the recirculation loop 32 such that the supply flow and the second flow combine to form a mixture and are then re-transported to the superfiltration membrane element. The concentration of the solute in the recirculation loop 32 increases as a function of time, and The pressure of the mixture increases as a function of time in the first operating mode, A second operating mode, The second flow or the mixture is transported directly to the waste outlet, and The configuration of the pressure vessel array 16 provides a second operating mode that results in a substantially uniform flushing profile of the solute concentration of the second flow with respect to time, and Methods that include...

9. Each of the aforementioned separate flow paths 76 has a hydraulic residence time, The hydraulic residence time of each of the separate flow paths 76 has a variance from the average of the hydraulic residence times of the separate flow paths 76. The dispersion of the liquid pressure residence time in each separate flow path 76 has a distribution and a standard deviation, and The method according to claim 8, wherein the standard deviation is less than 5 seconds, more preferably less than 4 seconds, and more preferably less than 3 seconds.

10. The method according to claim 8 or 9, wherein conductivity is measured in the recirculation loop at different times, the measured conductivity in the recirculation loop is reduced during the second operating mode, and the time it takes for the measured conductivity to decrease from 80% to 20% of the total conductivity range is less than 7 seconds.

11. The pressure vessel array 16 has a first pressure drop between the inlet port 24 and the outlet port 26 of one pressure vessel 20. The pressure vessel array 16 has a second pressure drop which is the maximum pressure difference between either the first end 25 of both of the two parallel pressure vessels 20 or the second end 27 of both of them. Furthermore, the method according to any one of claims 8 to 10, wherein the ratio of the first pressure drop to the second pressure drop is greater than 5:1, more preferably greater than 10:1, and more preferably greater than 15:

1.

12. The array inlet 86 and array outlet 88 are connected to a plurality of pressure vessel stack assembly sets 19 connected in parallel, and each pressure vessel stack assembly set 19 is An inlet header 60 connected to the array inlet 86 and an outlet header 62 connected to the array outlet 88, A first pressure vessel stack assembly 70, a last pressure vessel stack assembly 72, and at least one additional pressure vessel stack assembly 18 between them, wherein each pressure vessel stack assembly 18 in the set includes a stack inlet 22 connected to the inlet header 60 at a first end 25 and a stack outlet 30 connected to the outlet header 62 at a second end 27, A header inlet 64 positioned between the inlet header 60 and the array inlet 86, the header inlet 64 closest to the first pressure vessel stack assembly 70, A header outlet 66 positioned between the outlet header 62 and the array inlet 86, the header outlet 66 closest to the last pressure vessel stack assembly 72 and A filtration system according to any one of claims 1 to 7, wherein each pressure vessel 20 in the plurality of pressure vessel stack assembly sets 19 provides a separate flow path 76 in the recirculation loop 32, passing sequentially through the array inlet 86 and the array outlet 88.

13. A filtration system according to any one of claims 1 to 7 or 12, wherein a first pressure vessel assembly set 19 includes a first inlet header 60 and a first outlet header 62, and a second pressure vessel assembly set 19' includes a second inlet header 60' and a second outlet header 62', and (1) one or both pairs of the first inlet header 60 and the second inlet header 60', and (2) the first outlet header 62 and the second outlet header 62' are collinear, adjacent, and directly connected.

14. The first and second pressure vessel assembly sets (19, 19') and the corresponding first and second inlet headers (60, 60'), first and second outlet headers (62, 62'), first and second header inlets (64, 64'), and first and second header outlets (66, 66') are included, as follows: (1) The first and second header inlets (64, 64') are positioned between the first inlet header 60 and the second inlet header 60', or (2) The first and second header outlets (66, 66') are positioned between the first outlet header 60 and the second outlet header 62'. A filtration system according to any one of claims 1 to 6, 12, or 13, wherein exactly one of the following applies.

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