Design of fluidic manifolds in electrodialysis devices

Abstract

The present application relates to an electrochemical separation apparatus comprising a first electrode, a second electrode, a cell stack comprising alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode, an inlet manifold configured to introduce a fluid into one of the depletion compartments or the concentration compartments, an outlet manifold, and one or more of a fluid flow director disposed within the inlet manifold and having a surface configured to alter a flow path of the fluid introduced into the inlet manifold and direct the fluid into one of the depletion compartments or the concentration compartments, and a second fluid flow director disposed within the outlet manifold and having a surface configured to alter a flow path of the fluid introduced into the outlet manifold via one of the depletion compartments or the concentration compartments.

Description

[0001] This application is a divisional of application 201880039970.9, filed on June 20, 2018, entitled "Design of Fluidic Manifolds in Electrodialysis Devices". Related Applications

[0002] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Serial No. 62 / 522,732, filed on June 21, 2017, entitled "Design of Flow Directing Features Within the Fluidic Manifolds of Electrodialysis Devices", which is incorporated by reference herein in its entirety. TECHNICAL FIELD

[0003] Aspects and embodiments disclosed herein relate generally to electrochemical membrane systems and methods of operating the same. BACKGROUND

[0004] Discussion of Related Art

[0005] Devices that use electric fields to purify fluids can be used to treat water and other liquids containing dissolved ionic species. Two types of devices that treat water in this way are electrodialysis and electrodialysis reversal devices. Within these devices, concentrated compartments and dilute compartments are separated by ion-selective membranes. Electrodialysis devices typically include alternating electrically active semi-permeable anion exchange membranes and cation exchange membranes. The spaces between these membranes are configured to create liquid flow compartments with inlets and outlets. An applied electric field imposed via electrodes causes dissolved ions to migrate through the anion exchange membranes and cation exchange membranes that are attracted to their respective counter electrodes. This typically results in the liquid of the dilute compartments being depleted of ions, while the liquid in the concentrated compartments is enriched with the transferred ions.

[0006] Devices that are structurally similar to electrodialysis devices can be used as reverse electrodialysis (RED) devices. Two sets of compartments are fed with fluids of different ion concentrations separated by ion-selective membranes; for example, seawater and river water. The difference in concentration and chemical potential results in a voltage difference across each membrane, which when summed over the total number of membranes in the device, results in a voltage potential at the two electrodes bounding the stack of compartments and membranes. SUMMARY

[0007] According to one or more aspects, an electrochemical separation system can include a first electrode, a second electrode, a first electrochemical separation modular unit having a first cell stack defining a plurality of alternating depleted compartments and concentrated compartments supported by a first frame, the first electrochemical separation modular unit positioned between the first electrode and the second electrode, and a second electrochemical separation modular unit adjacent to and cooperating with the first electrochemical separation modular unit, having a second cell stack defining a plurality of alternating depleted compartments and concentrated compartments supported by a second frame, the second electrochemical separation modular unit positioned between the first electrochemical separation modular unit and the second electrode.

[0008] According to one or more aspects, a method of assembling an electrochemical separation system can include installing a first electrochemical separation modular unit having a first cell stack surrounded by a first frame in a vessel between a first electrode and a second electrode, and installing a second electrochemical separation modular unit having a second cell stack surrounded by a second frame in the vessel between the first electrochemical separation modular unit and the second electrode.

[0009] According to one or more aspects, an electrochemical separation modular unit can include a cell stack defining a plurality of alternating depleted compartments and concentrated compartments, and a frame surrounding the cell stack and including a manifold system configured to facilitate fluid flow through the cell stack.

[0010] According to one or more aspects, a flow distributor for electrochemical separation can include a plurality of first conduits oriented in a first direction and configured to deliver a feed to at least one compartment of an electrochemical separation apparatus, and a plurality of second conduits oriented in a second direction, the plurality of second conduits in fluid communication with the plurality of first conduits and with an inlet manifold associated with the electrochemical separation apparatus.

[0011] According to one or more aspects, an electrochemical separation system can include a first electrode, a second electrode, a first electrochemical separation modular unit including a plurality of alternating depleted compartments and concentrated compartments positioned between the first electrode and the second electrode, a second electrochemical separation modular unit including a plurality of alternating depleted compartments and concentrated compartments, and a spacer; the second electrochemical separation modular unit arranged in cooperation with the first electrochemical separation modular unit and positioned between the first electrochemical separation modular unit and the second electrode, the spacer disposed between and adjacent to the first and second electrochemical separation modular units, the spacer configured to reduce electrical current loss within the system.

[0012] According to one or more embodiments, a modular electrochemical separation system (which can also be referred to as an electrical purification apparatus or device) can improve the efficiency and overall flexibility of various treatment processes. In some embodiments, a cross-flow electrochemical separation apparatus (e.g., a cross-flow electrodialysis (ED) apparatus) can be implemented as an attractive alternative to conventional plate-and-frame apparatuses. Cross-flow apparatuses are described in US 8627560 B2, US 8741121 B2, and US 20160346737 Al, all of which are incorporated herein by reference in their entirety for all purposes. In some embodiments, current inefficiencies in a cross-flow electrochemical separation apparatus can be reduced. In at least certain embodiments, current inefficiencies due to current bypass through inlet and outlet manifolds can be addressed. Energy consumption and membrane requirements can also be reduced, both of which can impact life cycle costs in various applications. In some embodiments, a membrane utilization of at least 85% can be achieved. The reduction in membrane requirements, in turn, can result in a reduction in manufacturing costs, weight, and space requirements for the electrochemical separation apparatus.

[0013] In some specific embodiments, process efficiency of a cross-flow ED apparatus can be significantly improved. In some embodiments, efficiency of an electrochemical separation system can be improved for desalination of brackish water, seawater, and brine from oil and gas production. In at least some embodiments, cost competitiveness of ED can be improved compared to reverse osmosis (RO), which is currently the dominant technology for desalination.

[0014] One or more embodiments disclosed herein relate to an apparatus that can electrically purify a fluid, and methods of manufacturing and using the same, which can be contained within a housing. A liquid or other fluid to be purified enters the purification apparatus and is treated under the influence of an electric field to produce an ion-depleted liquid. Species from the incoming liquid are collected to produce an ion-concentrated liquid.

[0015] According to one or more embodiments, the electrochemical separation system or device can be modular. Each modular unit can generally function as a sub-block of the overall electrochemical separation system. The modular units can include any desired number of cell pairs. In some embodiments, the number of cell pairs per modular unit can depend on the total number of cell pairs and passes in the separation device. It can also depend on the number of cell pairs that can be thermally bonded and encapsulated in a frame and have an acceptable failure rate when tested for cross-leakage and other performance criteria. This number can be based on statistical analysis of the manufacturing process and can increase as process controls improve. In some non-limiting embodiments, the modular units can include from about 50 to about 100 cell pairs. The modular units can be assembled individually and subjected to quality control testing, such as leakage, separation performance, and pressure drop, before being incorporated into a larger system. In some embodiments, the cell stacks can be installed in a frame as modular units that can be tested independently. Multiple modular units can then be assembled together to provide the overall desired number of cell pairs in the electrochemical separation device. In some embodiments, the assembly method can generally involve placing a first modular unit on a second modular unit, placing a third modular unit on the first and second modular units, and repeating to obtain the desired number of multiple modular units. In some embodiments, the assemblies or individual modular units can be inserted into a pressure vessel for operation. Multiple-pass flow configurations are possible with blocking membranes and / or spacers placed between or within the modular units. The modular approach can improve manufacturability in terms of time and cost savings. Modularity can also facilitate system maintenance by allowing individual modular units to be diagnosed, isolated, removed, and replaced. The individual modular units can include manifold devices and flow distribution systems to facilitate the electrochemical separation process. The individual modular units can be in fluid communication with each other, as well as with a central manifold device and other systems associated with the overall electrochemical separation process.

[0016] According to one or more embodiments, the efficiency of an electrochemical separation system can be improved. Current loss is a potential source of inefficiency. In some embodiments, such as embodiments involving a cross-flow design, the potential for current leakage can be addressed. Current efficiency can be defined as the percentage of current that is effectively moved from the dilute stream to the concentrate stream. Various sources of current inefficiency can exist in an electrochemical separation system. One potential source of inefficiency can involve current that bypasses a cell pair by flowing through dilute and concentrate inlet and outlet manifolds. Opened inlet and outlet manifolds can be in direct fluid communication with the flow compartments and can reduce the pressure drop in each flow path. A portion of the current from one electrode to the other can bypass the stack of cell pairs by flowing through open areas. Bypass current reduces current efficiency and increases energy consumption. Another potential source of inefficiency can involve ions from the concentrate entering the dilute stream due to incomplete permselectivity of the ion exchange membranes. In some embodiments, techniques associated with sealing and packaging of the membranes and screens within the device can help reduce current leakage.

[0017] In one or more embodiments, bypass paths through the stack can be manipulated to promote current flow along direct paths through the cell stack, thereby improving current efficiency. In some embodiments, an electrochemical separation device can be constructed and arranged such that one or more bypass paths are more tortuous than direct paths through the cell stack. In at least certain embodiments, an electrochemical separation device can be constructed and arranged such that one or more bypass paths exhibit higher electrical resistance than direct paths through the cell stack. In some embodiments involving a modular system, individual modular units can be configured to improve current efficiency. Modular units can be constructed and arranged to provide current bypass paths that will help current efficiency. In non-limiting embodiments, modular units can include a manifold system and / or a flow distribution system configured to improve current efficiency. In at least some embodiments, a frame surrounding the cell stack in an electrochemical separation modular unit can be constructed and arranged to provide predetermined current bypass paths. In some embodiments, promoting a multi-pass flow configuration within an electrochemical separation device can help reduce current leakage. In at least some non-limiting embodiments, blocking membranes or spacers can be inserted between modular units to direct dilute and / or concentrate streams into a multi-pass flow configuration, thereby improving current efficiency. In some embodiments, a current efficiency of at least about 60% can be achieved. In other embodiments, a current efficiency of at least about 70% can be achieved. In still other embodiments, a current efficiency of at least about 80% can be achieved. In at least some embodiments, a current efficiency of at least about 85% can be achieved.

[0018] According to one or more aspects, an electrochemical separation device can include a cell stack. The cell stack can further include a plurality of aligned cell pairs, each of the plurality of aligned cell pairs including an ion concentrating compartment and an ion diluting compartment, the ion concentrating compartment being structured and arranged to provide fluid flow in a first direction, the ion diluting compartment being structured and arranged to provide fluid flow in a second direction different from the first direction.

[0019] According to one or more aspects, there is provided an electrochemical separation apparatus. The electrochemical separation apparatus includes a first electrode, a second electrode, a cell stack including alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode, an inlet manifold configured to introduce a fluid into one of the depletion compartments or the concentration compartments, an outlet manifold, and one or more of a fluid director disposed within the inlet manifold and having a surface configured to alter a flow path of the fluid introduced into the inlet manifold and direct the fluid into the one of the depletion compartments or the concentration compartments, and a second fluid director disposed within the outlet manifold and having a surface configured to alter a flow path of the fluid introduced into the outlet manifold via the one of the depletion compartments or the concentration compartments.

[0020] In some embodiments, the fluid flow path through the depletion compartments is perpendicular to the fluid flow path through the concentration compartments.

[0021] In some embodiments, the fluid director is disposed within the inlet manifold and is arranged to at least partially block shunt current through the inlet manifold. The fluid director can define a fluid flow path through the inlet manifold between different portions of the cell stack, the fluid flow path having a cross-sectional area that is less than a cross-sectional area of the inlet manifold.

[0022] In some embodiments, the cell stack has an average current efficiency of at least 85%.

[0023] In some embodiments, the cell stack includes a plurality of sub-blocks, and the fluid director includes a plurality of ramps arranged to direct the fluid into different respective ones of the plurality of sub-blocks. A gap of less than 1 mm can be defined between an edge of each of the ramps and the cell stack.

[0024] In some embodiments, the fluid director further includes a plurality of conduits fluidically isolated from one another. Each of the plurality of conduits terminates at a respective one of the plurality of ramps. A sum of cross-sectional areas of the plurality of conduits can be less than a cross-sectional area of the inlet manifold.

[0025] In some embodiments, the apparatus further includes a second fluid director disposed within the outlet manifold. The second fluid director can be configured to at least partially block shunt current through the outlet manifold.

[0026] In some embodiments, the device further includes: a second cell stack disposed between the cell stack and the second electrode, the second cell stack defining alternating second depleted compartments and second concentrated compartments; a second inlet manifold aligned with the outlet manifold and configured to introduce fluid from the outlet manifold into one of the second depleted compartments or the second concentrated compartments; a third fluidic diverter disposed within the second inlet manifold and having a surface configured to alter a flow path of fluid introduced into the second inlet manifold and direct the fluid into one of the second depleted compartments or the second concentrated compartments; a second outlet manifold disposed on an opposite side of the second cell stack from the second inlet manifold; and a bulkhead fluidically separating the inlet manifold from the second outlet manifold.

[0027] In some embodiments, the cell stack includes a plurality of sub-blocks, and the fluidic diverter includes a plurality of baffles arranged to isolate flow of fluid into each of the plurality of sub-blocks from flow of fluid into other ones of the sub-blocks. The fluidic diverter can further include a concentric fluid conduit.

[0028] In some embodiments, the fluidic diverter includes curved protrusions extending inward from a wall of the inlet manifold toward the cell stack. The fluidic diverter can reduce a cross-sectional area of the inlet manifold by a first amount at an end of the inlet manifold and reduce the cross-sectional area of the inlet manifold by a second amount greater than the first amount at a midpoint along a length of the inlet manifold. The fluidic diverter can be configured to reduce a flow rate of fluid through compartments in a central region of the cell stack.

[0029] In some embodiments, the device further includes a second fluidic diverter disposed within the outlet manifold. The second fluidic diverter can have a cross-sectional area that decreases along a flow path through the outlet manifold. The second fluidic diverter can be configured to reduce a pressure drop of fluid through the device.

[0030] In some embodiments, the device further includes a fluid inlet having a cross-section different from a cross-section of the inlet manifold and a fluid adapter disposed between the fluid inlet and the inlet manifold. The fluid adapter can include a conduit having a first portion with an inward taper in which a width of the conduit decreases in a first axis and a second portion with an outward taper in which the width of the conduit increases in a second axis, the first portion and the second portion not overlapping. The inward taper of the first portion of the conduit can be an elliptical taper.

[0031] In some embodiments, the device further includes a recirculation line configured to direct concentrated fluid that has passed through a concentrated compartment back into the concentrated compartment.

[0032] In some embodiments, the inlet manifold is divided into fluidically isolated conduits configured to direct predetermined amounts of fluid to different portions of the cell stack. The fluidically isolated conduits can have cross-sectional areas selected so that the fluid flow rate through the compartments in the central region of the cell stack is less than the fluid flow rate through the compartments in the upper and lower regions of the cell stack. The fluidically isolated conduits can have cross-sectional areas selected so that the fluid flow rate through the compartments in the upper region of the cell stack is substantially equal to the fluid flow rate through the compartments in the lower region of the cell stack.

[0033] According to one or more aspects, a method of improving current efficiency within an electrochemical separation device is provided, the electrochemical separation device comprising a cell stack defining alternating depleted compartments and concentrated compartments disposed between a first electrode and a second electrode, a fluid flow path through the depleted compartments being perpendicular to a fluid flow path through the concentrated compartments. The method comprises inserting a fluidic director into an inlet manifold of the device, the fluidic director having a surface configured to alter a flow path of fluid introduced into the inlet manifold and direct the fluid into one of a plurality of depleted compartments or a plurality of concentrated compartments and at least partially block a bypass current through the inlet manifold.

[0034] In some embodiments, the method further comprises increasing uniformity of fluid flow through the cell stack by installing a fluidic adapter on an inlet of the inlet manifold, the fluidic adapter comprising a conduit having a first portion and a second portion, the first portion having an inward taper in which a width of the conduit decreases in a first axis, the second portion having an outward taper in which the width of the conduit increases in a second axis, the first portion and the second portion not overlapping. The first axis can be perpendicular to the second axis.

[0035] In some embodiments, the method further comprises reducing a pressure drop through the device by installing a tapered fluidic director in an outlet manifold of the device.

[0036] In some embodiments, the method further comprises installing a second fluidic director in an outlet manifold of the device, the second fluidic director having a curved surface that narrows a flow path through the outlet manifold by a first amount at a midpoint along a length of the outlet manifold and narrows the flow path of the outlet manifold by a second amount that is less than the first amount near an end of the outlet manifold.

[0037] According to another aspect, an electrochemical membrane apparatus is provided. The electrochemical membrane apparatus includes a first electrode, a second electrode, a cell stack including alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode, an ion-selective membrane separating the depletion compartments from the concentration compartments, an inlet manifold configured to introduce a fluid into one of the depletion compartments or the concentration compartments, an outlet manifold, and one or more of a fluid director disposed within the inlet manifold and having a surface configured to alter a flow path of the fluid introduced into the inlet manifold and direct the fluid into the one of the depletion compartments or the concentration compartments, and a second fluid director disposed within the outlet manifold and having a surface configured to alter a flow path of the fluid introduced into the outlet manifold via the one of the depletion compartments or the concentration compartments.

[0038] In some embodiments, the apparatus is an electrodialysis apparatus for purifying a fluid using an electric field.

[0039] In some embodiments, the apparatus is a reverse electrodialysis apparatus for generating electrical energy from two or more fluid streams having different ion concentrations.

[0040] The following discussion of additional aspects, embodiments, and advantages of the example aspects and embodiments will be understood and appreciated by those skilled in the art in view of the following written specification, taken with the drawings, in which: BRIEF DESCRIPTION OF DRAWINGS

[0041] The drawings are not intended to be to scale. In the drawings, each identical, or nearly identical, component that is illustrated in various figures is represented with a like numeral. For purposes of clarity, not every component is called out in every drawing. In the drawings:

[0042] FIG. 1A An example of a sub-block of an electrodialysis apparatus is shown;

[0043] FIG. 1B A stack of four sub-blocks in a sub-block prior to insertion into an outer housing is shown; FIG. 1A

[0044] FIG. 1C An assembled ED apparatus with a transparent housing is shown;

[0045] FIG. 1D An assembled ED apparatus with an opaque housing is shown;

[0046] ​FIG. 1E Computational fluid dynamics (CFD) model of four sub-block ED devices is shown;

[0047] FIG. 2A Fluid is shown being delivered to the dilution compartments of the ED device via external piping to the adapter fittings;

[0048] FIG. 2B Fluid is shown being distributed in parallel to all dilution compartments of the ED device via the inlet manifold;

[0049] FIG. 2C Single pass configuration of the ED device is shown;

[0050] FIG. 2D Dual pass configuration of the ED device is shown;

[0051] FIG. 3 Non-ideal ED process with low efficiency and water loss is shown;

[0052] FIG. 4 Simplified model of current flow in the dilution or concentration pools of the ED device is shown;

[0053] FIG. 5 is a resistance network model for simulating current flow in the ED device;

[0054] FIG. 6 Calculation of the resistance to bypass current for a design with triangular ports is shown;

[0055] FIG. 7 is a chart showing an example of current efficiency as a function of cell pair position in the pass;

[0056] FIG. 8 is a chart showing an example of average current efficiency as a function of the number of cell pairs in the pass;

[0057] FIG. 9 is a chart showing an example of average current efficiency as a function of dilute feed concentration and the ratio of average concentration in the concentrate / average concentration in the dilute;

[0058] FIG. 10A is a cross section of the base design of the ED device;

[0059] FIG. 10B CFD simulation results of the flow in the stack of four sub-blocks of the base design of FIG. 10A

[0060] FIG. 10C is a plot showing vertical position versus flow rate through cell pairs in the base design of FIG. 10A

[0061] ​​FIG. 11A It shows FIG. 10A CFD simulation of the flow in the uppermost battery pair in the basic design;

[0062] FIG. 11B It shows FIG. 10A CFD simulation of the flow in the central battery pair in the basic design;

[0063] FIG. 11C It shows FIG. 10A CFD simulation of the flow in the bottommost battery pair in the basic design;

[0064] FIG. 12A The flow guidance characteristics for an ED device in the form of a tubular conduit are shown;

[0065] FIG. 12B The flow guidance characteristics for an ED device in the form of a concentric tubular conduit with baffles are shown;

[0066] FIG. 12C Additional flow characteristics for ED devices in the form of concentric tubular conduits with baffles are shown;

[0067] FIG. 12D The flow guiding characteristics of an ED device in the form of a parallel conduit with baffles and ramps are shown;

[0068] FIG. 12E Other flow guiding features of the ED device in the form of a parallel conduit with baffles and ramps are shown;

[0069] FIG. 13A It shows FIG. 10A The configuration of the manifold in the basic design;

[0070] FIG. 13B An improved manifold is shown, featuring enhanced current efficiency and improved flow distribution.

[0071] FIG. 14 This is a graph illustrating an example of current efficiency relative to battery pair location in a single-path ED device with four electrically isolated sub-blocks;

[0072] FIG. 15A Side, front, top, and isometric views of a manifold insert for an ED device are shown, the manifold insert including a fluid conduit defined by a linear profile baffle and an elliptical ramp;

[0073] FIG. 15B It shows including FIG. 15A CFD model of the manifold ED device;

[0074] FIG. 15C The manifold and basic design shown in Figure 10 are illustrated. FIG. 15AComparison between manifolds;

[0075] FIG. 15D shows a manifold insert for use in an ED device having eight sub-blocks FIG. 15A view of a single piece modification of a manifold insert of

[0076] FIG. 15E shows a manifold insert for use in an ED device having eight sub-blocks FIG. 15A view of a two piece modification of a manifold insert of

[0077] FIG. 15F shows a manifold of an eight sub-block ED device having a base design and including FIG. 15D Comparison between eight block ED devices with four manifold inserts of

[0078] FIG. 16A shows CFD simulations of component Z-velocity through the central ZY plane and through the top, middle and bottom ZX planes for the base and optimized designs at a flow rate of 4 m 3 / hr;

[0079] FIG. 16B shows CFD simulations of component Z-velocity through the central ZY plane and through the top, middle and bottom ZX planes for the base and optimized designs at a flow rate of 10 m 3 / hr;

[0080] FIG. 16C shows CFD simulations of component Z-velocity through the central ZY plane for the base and optimized designs shown in FIG. 15F

[0081] FIG. 16D shows a relationship of process efficiency versus current (fluid flow rate) for the base and optimized designs shown in FIG. 15F

[0082] FIG. 17A is a graph of results of CFD simulations of flow rate per cell pair at different heights (Y axis positions) for the base and optimized designs of an ED device at a flow rate of 4 m 3 / hr;

[0083] FIG. 17B is a graph of results of CFD simulations of flow rate per cell pair at different heights (Y axis positions) for the base and optimized designs of an ED device at a flow rate of 10 m 3 / hr;

[0084] FIG. 18A ​​is a heat map of the voltage drop distribution across the cell for the base ED system design;

[0085] FIG. 18B is a heat map of the voltage drop distribution across the cell for the optimized ED system design;

[0086] FIG. 19A shows the measurement locations for voltage drop versus flow rate in the CFD simulations for the base and optimized ED system designs;

[0087] FIG. 19B is a plot of the results of the CFD simulations of voltage drop versus flow rate for the different sub-blocks in the base ED system design;

[0088] FIG. 19C is a plot of the results of the CFD simulations of voltage drop versus flow rate for the different sub-blocks in the optimized ED system design;

[0089] FIG. 20A shows a cross-section of the initial design of the manifold of the ED device;

[0090] FIG. 20B shows a cross-section of an alternative design of the manifold of the ED device;

[0091] FIG. 20C shows a cross-section of an alternative design of the manifold of the ED device;

[0092] FIG. 20D shows a cross-section of an alternative design of the manifold of the ED device;

[0093] FIG. 21 shows the simulated process efficiency for FIGS. 20A-20C the manifold design in the middle;

[0094] FIG. 22 shows the results of the CFD simulations for the ED device of Figure 20 in the cells at the top, middle and bottom of the stack of cells of the ED device;

[0095] FIG. 23A is a cross-section of an ED module with four sub-blocks in a two-pass configuration;

[0096] FIG. 23B is a cross-section of an ED module with four sub-blocks in a two-pass configuration with curved protrusion inserts installed in the manifold;

[0097] FIG. 24A shows the simulated results of the pressure distribution through the center of the module of FIG. 23A ;

[0098] FIG. 24B shows the simulated results of the pressure distribution through the center of the module of FIG. 23Bsimulation results of the pressure distribution in the center of the entire module;

[0099] FIG. 25 shows the simulation results of the velocity distribution in the center of the entire module; FIG. 23B

[0100] FIG. 26 shows the simulation results of the mass flow profile (per cell pair) through the module of FIG. 23A and FIG. 23B

[0101] FIG. 27 shows several examples of possible outlet manifold inserts;

[0102] FIG. 28 is a cross section of the first pass of an ED module with four sub-blocks in a two-pass configuration, with a curved protrusion insert installed in the inlet manifold and a straight conical insert installed in the outlet manifold;

[0103] FIG. 29 shows the simulation results of the mass flow profile (per cell pair) through the module of FIG. 28 with and without outlet manifold inserts;

[0104] FIG. 30 is a plot of the process efficiency versus the ratio of the average concentration of the concentrate to the dilute in an ED device as shown in FIG. 20B and an ED device as shown in FIG. 23B ;

[0105] FIG. 31A shows the fluid flow through the outlet manifold of an ED device without an outlet manifold insert;

[0106] FIG. 31B shows the fluid flow through the outlet manifold of an ED device with a tilted outlet manifold insert;

[0107] FIG. 32A is a table showing the effect of a tilted shaped outlet insert on the pressure drop over the ED module in a first example;

[0108] FIG. 32B is a table showing the effect of a tilted shaped outlet insert on the pressure drop over the ED module in a second example;

[0109] FIG. 33 is a cross section of an ED device with a fluid adapter set between the inlet manifold and the external piping;

[0110] FIG. 34A is an isometric view of a basic embodiment of a non-optimized fluid adapter for an ED device;​​

[0111] FIG. 34B is a partial transparent view of the fluid adapter of FIG. 34A

[0112] FIG. 34C is a top-down view of the fluid adapter of FIG. 34A

[0113] FIG. 34D is a bottom-up view of the fluid adapter of FIG. 34A

[0114] FIG. 34E is a cross-section through the first axis of the fluid adapter of FIG. 34A

[0115] FIG. 34F is a cross-section through the second axis of the fluid adapter of FIG. 34A

[0116] FIG. 35A is an isometric view of an embodiment of an improved fluid adapter for an ED device;

[0117] FIG. 35B is a partial transparent view of the fluid adapter of FIG. 35A

[0118] FIG. 35C is a cross-section through the first axis of the fluid adapter of FIG. 35A

[0119] FIG. 35D is a cross-section through the second axis of the fluid adapter of FIG. 35A

[0120] FIG. 36A shows simulation results of fluid flow through an inlet manifold of an ED device comprising the fluid adapter of FIG. 34A

[0121] FIG. 36B shows simulation results of fluid flow through an inlet manifold of an ED device comprising the fluid adapter of FIG. 35A

[0122] FIG. 37A shows simulation results of the component Z-velocity distribution of fluid through a cell in an ED device comprising the fluid adapter of FIG. 34A

[0123] FIG. 37B shows simulation results of the component Z-velocity distribution of fluid through a cell in an ED device comprising the fluid adapter of FIG. 35A DETAILED DESCRIPTION ​​​​​​​​​​​​

[0124] The aspects and embodiments disclosed herein are not limited to the details of the components and arrangements for the process described in the following description or illustrated in the drawings. The aspects and embodiments disclosed herein are capable of other embodiments and of being practiced or carried out in various ways.

[0125] Electrodeionization (EDI) is a process that uses electroactive media and electrical potential to affect the transport of ions to remove or at least reduce one or more ionized or ionizable species from water. The electroactive media is typically used to alternately collect and discharge ionic and / or ionizable species, and in some cases, to facilitate the transport of ions through ion or electron substitution mechanisms, which can be continuous. EDI devices can include electrochemically active media that are permanently charged or temporarily charged, and can be operated batch-wise, intermittently, continuously, and / or even in a reverse polarity mode. EDI devices can be operated to facilitate one or more electrochemical reactions that are specifically designed to achieve or enhance performance. Furthermore, such electrochemical devices can include electroactive membranes, such as semi-permeable or selectively permeable ion exchange membranes or bipolar membranes. Continuous electrodeionization (CEDI) devices are EDI devices known to those skilled in the art that are operated in a manner in which water purification can be continuously performed as ion exchange materials are continuously recharged. CEDI technology can include processes such as continuous deionization, filled cell electrodialysis, or electrodiaresis. In a CEDI system, under controlled voltage and salinity conditions, water molecules can be split to generate hydrogen or hydronium ions or species and hydroxide or hydroxyl ions or species, which can regenerate ion exchange media in the device and thus facilitate the release of captured species therefrom. In this manner, a water stream to be treated can be continuously purified without the need for chemical recharging of ion exchange resins.

[0126] Electrodialysis (ED) devices operate on similar principles as CEDI, except that ED devices typically do not contain electroactive media between the membranes. Due to the lack of electroactive media, operation of ED based on low salinity feed water can be hindered by elevated electrical resistance. Furthermore, because operation of ED on high salinity feed water can result in elevated current consumption, ED devices have been most effectively used to date for moderate salinity source waters. In ED based systems, because there is no electroactive media, splitting water is inefficient, and operation in such a regime is typically avoided.

[0127] In CEDI and ED devices, a plurality of adjacent cells or compartments are typically separated by a selectively permeable membrane that allows either positively charged species or negatively charged species to pass, but not both. In such devices, diluting or depleting compartments are typically interspaced with concentrating compartments or concentration compartments. In some embodiments, a cell pair can refer to a pair of adjacent concentrating and diluting compartments. As water flows through the depleting compartments, ions and other charged species can typically be drawn into the concentrating compartments under the influence of an electric field, such as a DC field. Positively charged species are drawn toward a cathode, which is typically located at one end of a stack of depleting and concentration compartments, while negatively charged species are likewise drawn toward an anode, which is typically located at an opposite end of the stack of compartments of such a device. The electrodes are typically housed in electrolyte compartments, which are typically partially isolated from fluid communication with the depleting and / or concentration compartments. Once in the concentration compartments, the charged species are typically captured by a barrier of the selectively permeable membrane that at least partially defines the concentration compartments. For example, anions are typically prevented from further migrating away from the concentration compartments by a cation-selective membrane. Once captured in the concentrating compartments, the captured charged species can be removed in a concentrated stream.

[0128] In CEDI and ED devices, a DC field is typically applied to the cells from a source of voltage and current applied to the electrodes (anode or positive electrode, and cathode or negative electrode). The voltage and current source (collectively, the "power supply") can itself be powered by a variety of means, such as an AC power source or a power source derived from, for example, solar, wind, or wave energy. At the electrode / liquid interface, electrochemical half-cell reactions occur that initiate and / or facilitate the transfer of ions through the membranes and compartments. The particular electrochemical reactions that occur at the electrode / interface can be controlled to some extent by the salt concentration in the dedicated compartments that house the electrode assemblies. For example, a feed of sodium chloride to a high anode electrolyte compartment will tend to generate chlorine gas and hydrogen ions, while such a feed to a cathode electrolyte compartment will tend to generate hydrogen gas and hydroxide ions. Typically, the hydrogen ions generated at the anode compartment will combine with free anions, such as chloride ions, to maintain charge neutrality and produce a hydrochloric acid solution, and similarly, the hydroxide ions generated at the cathode compartment will combine with free cations, such as sodium ions, to maintain charge neutrality and produce a sodium hydroxide solution. The reaction products of the electrode compartments, such as the chlorine gas and sodium hydroxide generated, can be used in the process as needed for disinfection purposes, for membrane cleaning and decontamination purposes, and for pH adjustment purposes.

[0129] Plate-and-frame and spiral-wound designs have been used for various types of electrochemical deionization equipment, including but not limited to electrodialysis (ED) and electrodeionization (EDI) equipment. Commercially available ED equipment typically has a plate-and-frame design, while EDI equipment is available in both plate-and-frame and spiral configurations.

[0130] A "cross-flow" electrodialysis (ED) device has been described in previous patents, in which dilute and concentrate streams flow in perpendicular directions. The stack of cell pairs in the device can be assembled from one or more modular units, referred to as sub-blocks. FIG. 1A An example of a sub-block is shown. FIG. 1B A stack of four sub-blocks is shown prior to insertion into a housing. The term "cell stack" as used herein refers to a single sub-block or to a stack of multiple sub-blocks. FIG. 1C An assembled ED device with a transparent housing is shown. FIG. 1D An assembled ED device with an opaque housing is shown. FIG. 1E A computational fluid dynamics (CFD) model of a four-sub-block ED device is shown.

[0131] As shown, FIG. 2A fluid can be delivered into the dilute compartments of the ED device via external piping to adapter fittings. Then, as shown, FIG. 2B fluid is distributed among all dilute compartments in parallel via inlet manifolds. Similarly, product from all dilute compartments can be collected in outlet manifolds and delivered to external piping via adapter fittings. Flow to and from concentrate compartments can be similarly arranged. This flow configuration is commonly referred to as "single-pass". FIG. 2C A single-pass configuration of an ED device is shown.

[0132] Using baffles, flow through dilute and concentrate compartments can be arranged in a serpentine manner. For example, FIG. 2D A "two-pass" arrangement for dilute stream flow is shown, and more passes can be achieved by adding baffles. Multiple passes in the device increase flow path length, residence time, ion transfer, and ion removal, while still keeping velocity within an optimal process range.

[0133] Current efficiency for a cell pair in an ED device can be defined as follows:

[0134] (1)

[0135] where:

[0136] q di = flow rate per dilute compartment at the inlet

[0137] q do = flow rate per dilute compartment at the outlet

[0138] C i = concentration of ion i

[0139] η i = current efficiency

[0140] |z i = absolute value of the valence of ion i (e.g., for Na + z i = -1)

[0141] F = Faraday's constant = 96485 coulombs / equivalent

[0142] I = current

[0143] subscript in = at the inlet, out = at the outlet

[0144] In an ideal ED device, all of the applied current flows in series through each cell pair, the ion exchange membranes have perfect selectivity, there is no mechanical cross-leakage between the dilute and concentrate solutions, and there is no external leakage. Thus, the current efficiency, defined by Equation 1, is 100%.

[0145] In a real ED device, the current efficiency will not be 100% because the membranes do not have perfect selectivity. For example, a cation exchange membrane with a selectivity of 98% will result in about 98% of the current carried by cations being transferred from the dilute to the concentrate solution, while 2% of the current carried by anions is transferred from the concentrate back to the dilute solution. Thus, the current efficiency will be reduced by about 2%. Mechanical cross-leakage from the concentrate to the dilute solution also reduces the net ion transfer rate from the dilute solution, thus reducing the overall current efficiency. In addition, because the solutions flowing into and out of the cell pairs through the inlet and outlet manifolds are electrically conductive, a portion of the current will bypass the cell pairs by flowing through the manifolds; it does not participate in ion transfer, so the current efficiency is reduced. FIG. 3 An example of a non-ideal ED process is shown, where the location of the current bypass is indicated by the dashed oval.

[0146] A resistive network model was developed to simulate the current bypass and estimate the current efficiency under different operating conditions in an ED device. The model simply assumes that the current flow in a dilute or concentrate cell is as shown in FIG. 4 , where the arrows indicate the current flow. FIG. 5 The network model for a cell pair is shown in DP , which represents the Donnan potential across the membrane that must be included in the voltage drop across the cell pair.

[0147] The current through the network can be calculated using FIG. 6Equation 2 in the Appendix to calculate the resistance in the channel of the ED device. The resistance increases with decreasing channel width, increasing distance between the manifold and the active membrane area, decreasing liquid conductivity, and / or decreasing channel thickness. The resistance in the manifold slice corresponding to a cell pair can likewise be calculated using Equation 3 in the Appendix FIG. 6 . The resistance increases with decreasing cross-sectional area of the manifold, decreasing liquid conductivity, and / or increasing thickness of the manifold slice.

[0148] As the resistance of the channel and / or manifold increases, the current bypassing each cell pair decreases, and a greater portion of the total current will preferentially flow through the active membrane area, becoming effective in ion transfer.

[0149] Simulations have been performed and indicate that the highest current efficiency is that of the single sub-block in the pass. The current efficiency varies within the pass and is highest in the cell pairs at the ends and lowest in the cell pairs in the middle. (See FIG. 7 ). The average current efficiency decreases with increasing number of cell pairs in the pass. (See FIG. 7 and FIG. 8 ). The current efficiency is a function of the applied current, dilute and current flow rates, dilute and concentrate inlet concentrations, and temperature. (See FIG. 8 ). The current efficiency decreases linearly with increasing ratio of average concentrate concentration to average dilute concentration. (See FIG. 9 ). The average concentrations are each a mathematical average of the inlet and outlet concentrations.

[0150] A CFD model was developed for the four sub-block, single-pass, cross-flow ED device described above as shown in FIG. 2A and FIG. 2B . This model will hereafter be referred to as the base design.

[0151] FIG. 10A A center cross-section of the base design is shown. To simplify the calculations, every 100 cell pair sub-block was divided into 10 sections; each section representing 10 cell pairs. Flow simulations were then performed on this geometry. From the plot shown in FIG. 10B it can be seen that the Z-component of the flow velocity through each cell in the ZY plane is not uniform, resulting in a variation in flow rate per cell pair as shown in FIG. 10C . The flow rate per cell pair is lowest at the top cell pairs near the fluid inlet of the manifold.

[0152] The distribution of Z-velocity was further characterized using ZX cross-sectional planes through the top, middle, and bottom of the stack ( FIGS. 11A-11C ), where the overall Z-velocity of the top cross-section is approximately half that of the bottom.

[0153] like FIG. 7 As shown, the current efficiency is highest in the cell pairs at the top and bottom of the pathway, resulting in the highest proportion of current flowing through the membrane. Higher current densities increase the risk of current limiting and scaling in the low-flow-rate region. Furthermore, the lower flow rate through the initial dilution cells in the pathway will prevent these cells from operating at their highest current efficiency to remove salt. Therefore, it is advantageous to ensure that all cell pairs are optimized for flow rates.

[0154] As previously discussed, the proportion of applied current bypassing the battery pair stack through the manifold can be reduced by increasing the resistance in the channels and manifold. Previous designs have been proposed to reduce current bypass by decreasing the cross-sectional area of ​​the inlet and outlet manifolds. While effective in improving current efficiency, these changes result in increased voltage drops through the manifold and across the ED device.

[0155] FIG. 7 and FIG. 8 The results show that current efficiency decreases as the number of battery pairs electrically connected to a common manifold increases.

[0156] In an ideal design for a fluid manifold, fluid resistance will be minimized while resistance to bypass current will be maximized. This can be achieved by operating sub-blocks in parallel but electrically isolated from each other (except through the battery pair).

[0157] Therefore, the technical challenges are to reduce current bypass within a single sub-block, reduce current bypass through the fluid manifold between sub-blocks, ensure sufficient flow in the path to the first battery pair, improve flow distribution among all battery pairs in the path, and minimize the stress required to operate such an ED device. The aspects and embodiments disclosed herein include structures and methods for addressing these challenges.

[0158] The aspects and embodiments disclosed herein include flow guidance features that can be configured within the fluid manifold of an ED device to maximize current efficiency, standardize flow distribution, and minimize pressure drop.

[0159] As used herein, a flow-guiding feature or fluid guide may include, or be composed of, any conduit, channel, ramp, pipe, tube, baffle, blade, or other embodiment. The profile of these features may be a mathematical function (e.g., linear, polynomial, trigonometric, logarithmic, conic section) or freely generated.

[0160] The design of a fluid manifold can consist of the aforementioned features forming one or more conduits that guide one or more sub-blocks, and the flow rate within each conduit can be further subdivided by using additional flow guiding features.

[0161] Manufacture of these features can be accomplished by any of a variety of techniques, including but not limited to: 3D printing, CNC machining, or injection molding.

[0162] Examples of fluid flow directors can include: tubular fluid conduits ( FIG. 12A ), concentric tubular fluid conduits 1215 with baffles 1205 ( FIG. 12B and FIG. 12C ), and parallel conduits 1225 with walls 1220 and ramps 1230 ( FIG. 12D and FIG. 12E ).

[0163] As shown in FIG. 12B , pairs of baffles 1205 can define different fluid delivery zones 1210 along the length of the fluid flow director. In other embodiments, for example, as shown in FIG. 12B , multiple baffles 1205 can be included in a single fluid delivery zone 1210. Individual concentric tubular conduits 1215 (which, in other embodiments, can have cross-sections other than circular) can deliver fluid to different fluid delivery zones 1210. In some embodiments, the lowermost fluid delivery zone 1210L can not include a fluid conduit 1215. Each fluid delivery zone 1210 can deliver fluid to a single sub-module or sub-block (SB1, SB2, SB3, SB4 in FIG. 13A and FIG. 13B ) of a battery stack. The size (e.g., diameter) of the concentric tubular conduits 1215 and the space between adjacent concentric tubular conduits 1215 can be selected to deliver a predetermined amount of fluid to different sub-blocks or different zones of a battery stack. In some embodiments, the size of the concentric tubular conduits 1215 is selected so that the same amount or substantially the same amount of fluid flow or fluid flow rate is provided to different sub-blocks or different zones of a battery stack. In other embodiments, the size of the concentric tubular conduits 1215 is selected so that the same amount or substantially the same amount of fluid flow or fluid flow rate is provided to a subset of sub-blocks or zones, for example, in the upper and lower regions of a battery stack, while a different amount (e.g., a lesser amount) of fluid flow or fluid flow rate is provided to other sub-blocks or zones in the battery stack, for example, in the central region of the battery stack.

[0164] As shown in FIG. 12D , embodiments of fluid flow directors can include a ramp 1230 at the lower end of a conduit 1225 defined by a wall 1220. The conduit 1225 can terminate at the ramp 1230. The ramp 1230 can be formed by a region of the wall 1220 that curves toward the battery stack, with an axis of curvature on the battery stack side of the wall 1220 ( FIG. 12D ), or with an axis of curvature opposite the battery stack side of the wall 1220.FIG. 12E ). In some embodiments, as shown in FIG. 13B , the ramps 1230 can be horizontally disposed plates that intersect the walls 1220 at an angle of substantially 90°. In other embodiments, as shown in FIG. 15A , the walls 1220 can form the ramps 1230 by being curved along their entire length or substantially their entire length. Also as shown in FIG. 15A , additional walls 1220 can divide the fluid delivery region 1210 defined by the ramps 1230 into two or more sections.

[0165] The dimensions (e.g., length, width, and / or cross-sectional area) of the conduits 1225 can be selected to deliver a predetermined amount of fluid to different sub-blocks or different regions of the battery stack. In some embodiments, the dimensions of the conduits 1225 are selected such that the same amount or substantially the same amount of fluid flow or fluid flow rate is provided to different sub-blocks or different regions of the battery stack. In other embodiments, the dimensions of the conduits 1225 are selected such that the same amount or substantially the same amount of fluid flow or fluid flow rate is provided to a subset of sub-blocks or regions, e.g., in the upper and lower regions of the battery stack, while a different amount (e.g., a lesser amount) of fluid flow or fluid flow rate is provided to other sub-blocks or regions in the battery stack, e.g., in the central region of the battery stack.

[0166] In the basic design shown in FIG. 10A , the inlet manifold has an initial cross-sectional area A i and a stack height H i ( FIG. 13A ). In the embodiment shown in FIG. 13B , the flow manifold is divided into four conduits 1225 having cross-sectional areas A1, A2, A3, and A4. The conduits are formed by internal baffles or walls 1220 that are bent at the bottom to form ramps 1230 that can contact the interfaces between the sub-blocks SB1, SB2, SB3, and SB4. Thus, each conduit 1225 is in fluid communication with only one sub-block. FIG. 12C , FIG. 12D or FIG. 13B , the conduits 1225 or the conduits defined between or within the different concentric tubes 1215 in FIG. 12A and FIG. 12B may be fluidically isolated from each other. FIG. 12C , FIG. 12D or FIG. 13B , the sum of the cross-sectional areas of the conduits 1225 or the conduits defined between or within the different concentric tubes 1215 in FIG. 12A and FIG. 12B may be less than the cross-sectional area of the flow manifold.

[0167] In other embodiments, the ramp 1230 of the fluid director can not extend all the way to the cell stack, but can terminate at a distance from the cell stack, for example between 0.5 mm and 2 mm, less than 2 mm (or about 2 mm), less than 1 mm (or about 1 mm), or less than 0.5 mm (or about 0.5 mm), and form a gap of these dimensions between the ramp 1230 and the cell stack. The gap can facilitate insertion or removal of the fluid director from the flow manifold. The fluid director can thus define a fluid flow path through the flow manifold between different portions of the cell stack, the fluid flow path having a cross-sectional area that is smaller than a cross-sectional area of the flow manifold.

[0168] In FIG. 13B The configuration shown (hereinafter referred to as the "optimized design") limits the flow of current from one sub-block to another via the manifold. Within each sub-block, current can still pass through the manifold portion in fluid communication with that sub-block to bypass the cell stack. To calculate current efficiency, each sub-block can thus be modeled as if it were an ED device with only one sub-block. FIG. 14 Results of the current efficiency calculation for a device with four sub-blocks are shown; the average current efficiency is equal to FIG. 7 the current efficiency of a single sub-block.

[0169] In various embodiments, the ED devices disclosed herein can include one or more of a fluid director disposed within the inlet manifold and having a surface configured to alter a flow path of fluid introduced into the inlet manifold and direct the fluid into one of the depletion or concentration compartments, and a second fluid director disposed within the outlet manifold and having a surface configured to alter a flow path of fluid introduced into the outlet manifold via one of the depletion or concentration compartments.

[0170] FIG. 15A A non-limiting embodiment of the optimized design is shown, which includes a fluid conduit defined by a linear profile baffle and an elliptical ramp. The optimized design includes FIG. 15A The structure of the baffle and ramp shown can be formed as an insert that can be removably inserted into the manifold of a base design. FIG. 15B The optimized design is shown when incorporated into a CFD model. FIG. 15C A comparison of the center cross-section of the ED device for both the base design and the optimized design is shown. In the optimized design, the conduit is electrically isolated and is hydraulically parallel.

[0171] FIG. 15A The optimized design of FIG. 15B and FIG. 15C four sub-blocks. For example, FIG. 15DA one-piece design is shown for eight sub-block inserts, while FIG. 15E A two-piece design is shown for eight sub-block inserts. FIG. 15D and FIG. 15E These designs are shown in isometric, top, bottom, back, side, and front views. In the eight sub-block design, the small conduits 1505 stay in the back of the manifold, cut off flow at each individual ramp 1510 down the back of the insert. In contrast to the curved ramps of the embodiments shown in FIG. 12D , FIG. 12E and FIG. 15A The ramps in the embodiments shown in FIG. 15D and FIG. 15E are substantially planar. The term "ramp" as used herein includes curved and planar or flat ramps.

[0172] FIG. 15F A comparison of the central cross-sections of the eight sub-block ED devices is shown for both the base design and the optimized design.

[0173] As discussed above, the distribution of flow was simulated at different operating flow rates, and then optimized using CFD software. The component Z-velocity, flow rate per average cell pair, and pressure drop were then characterized.

[0174] FIG. 16A and FIG. 16B The component Z-velocity through the central ZY plane and through the top, middle, and bottom ZX planes is shown for the base design and the optimized design of 3 with device flow rates of 4 m 3 / hr and 10 m FIGS. 15A-15C / hr, respectively. For the base design, the Z-velocity through the central ZY plane varied approximately 2-4 times as much as the Z-velocity in the top, middle, and bottom ZX planes at all flow rates. In contrast, for all flow rates in the optimized design, the Z-velocity appeared constant across all planes.

[0175] FIG. 16C CFD simulations of the component Z-velocity through the central ZY plane are shown for the base design and the optimized design shown in FIG. 15F The Z-velocity through the central ZY plane of the optimized design was generally more uniform than that of the base design. FIG. 16D The process efficiency versus current (fluid flow rate) is shown for the base design and the optimized design shown in FIG. 15F For each of the fluid flow rates measured, the process efficiency of the optimized design was approximately 5% higher than that of the base design.

[0176] FIG. 17Ais a graph of CFD simulation results for the flow rate per cell pair at different heights (Y-axis positions) for a basic design and an optimized design of an ED device at a flow rate of 4 m 3 / hr. The basic design and the optimized design are described in more detail above. For the optimized design, the flow rate per cell pair is more uniform. FIG. 17B is a graph of CFD simulation results for the flow rate per cell pair at different heights (Y-axis positions) for a basic design and an optimized design of an ED device at a flow rate of 10 m 3 / hr. The basic design and the optimized design are described in more detail above. For the optimized design, the flow rate per cell pair is more uniform.

[0177] FIG. 18A and FIG. 18B show the pressure distribution at the center cross section in percent of the maximum pressure. In the basic design ( FIG. 18A ), the inlet pressure of the sub-blocks is uniform, while the outlet pressure varies such that the pressure drop across the sub-blocks increases from the top sub-block to the bottom sub-block (see also FIG. 19B ). In the optimized design ( FIG. 18B ), the inlet and outlet pressure of the sub-blocks varies such that the pressure drop across the sub-blocks is almost uniform (see also FIG. 19C ).

[0178] FIG. 19A show the locations of the pressure measurements used in the CFD simulation and define the pressure difference for the individual sub-blocks and the entire device. FIG. 19B and FIG. 19C show the variation of the pressure drop across sub-blocks 1 to 4 for different feed flow rates. As expected, the distribution of the flow rate per cell pair is more uniform in the optimized design, the pressure drop is more uniform.

[0179] In another aspect, features are provided that improve the flow distribution between cell pairs in the channel. In the existing cross-flow device manufactured by Evoqua Water Technologies, the cross section of the inlet and outlet manifolds is roughly triangular, as shown in FIG. 4 . An adapter fitting transfers the feed flow from the pipe to the inlet manifold. This design will be referred to as the initial design.

[0180] FIG. 10B and FIG. 10C show the results from a CFD simulation of the flow in a stack of four sub-blocks, each with 100 cell pairs. The flow is distributed unevenly among the cells. A comparison of the flow velocity distribution on three horizontal planes (one close to the inlet of the manifold, one in the middle of the stack, and one at the bottom of the stack) shows that the flow through the first few cell pairs is low, with a relatively large low-velocity zone (see FIGS. 11A-11C ).

[0181] As shown in FIG. 7The current efficiency is highest (and thus the proportion of the current that flows through the membrane is highest) at the cell pairs at both ends of the passageway, as shown earlier. The higher current density that results from this increases the risk of current limiting and fouling in the low flow rate zones. The lower flow rates through the first few dilution cells in the passageway will also mean that the potential of the higher current efficiency to remove salt is not fully utilized.

[0182] Thus, the technical challenge is to reduce the current bypass through the inlet and outlet manifolds, and to improve the flow distribution between the cell pairs in the passageway, particularly to ensure that there is sufficient flow to the first few cell pairs.

[0183] Disclosed herein are designs for the inlet and outlet flow manifolds in an ED device to improve the current efficiency and the flow distribution to the cell pairs.

[0184] As discussed earlier, the current efficiency in the cell pairs can be increased by increasing the electrical resistance in the inlet and outlet channels and manifolds. Starting with the initial design as shown in FIG. 20A there are alternative designs that can increase the current efficiency for a manifold cross-sectional area A1 and a distance L1 from the edge of the active membrane area to the edge of the manifold. For example, as shown in FIG. 20B a smaller manifold will increase the electrical resistance in the channels with a distance L2 > L1, and also increase the electrical resistance in the manifold with A2 < A1. As shown in FIG. 20C a smaller manifold will increase the electrical resistance in the manifold with A3 < A1. In the case where L3 = L1, the electrical resistance in the channels will not change. An isosceles trapezoidal cross-section with “wings” is shown in FIG. 20D FIG. 20D The cross-sectional area of the manifold of FIG. 20B is smaller than the cross-sectional area in FIG. 6 , while the average distance of the manifold from the active area is approximately the same.

[0185] FIG. 21 shows the process efficiency for the manifold designs in FIGS. 20A-20C . As expected, the process efficiency increases with the decrease in the cross-sectional area of the manifold, and the two designs with the same smaller area have similar efficiency. The process efficiency is related to the current efficiency, and is defined by the equation in FIG. 21

[0186] FIG. 22 shows that the flow distribution between the cell pairs in the initial design is uneven. The cell pairs near the top of the cell stack have lower feed flow rates than the cell pairs at lower positions in the cell stack.

[0187] ​​In the initial design, one potential solution to increase the uniformity of the flow through the different cells is to incorporate protrusions into the manifold to influence the flow distribution of cell pairs in the passageway. The protrusions can be wedges, vanes, baffles, bumps, or combinations thereof. The protrusions can also have holes or slots to allow a portion of the flow to pass directly through, reducing the vortices or eddies downstream.

[0188] In FIG. 23A and FIG. 23B a comparison between the existing design and a design including protrusions in the inlet manifold of a dual-pass ED device is shown, where in FIG. 23B a design including protrusions 2305 is presented. The profile of each protrusion 2305 is an arc that extends from the beginning of the manifold to the end. The arc can be circular or elliptical, or it can be freeform. As used herein, the term “fluidic director” includes embodiments such as the protrusions 2305.

[0189] CFD analysis was performed on the two ED devices shown in FIG. 23A and FIG. 23B Each ED device has four sub-stacks arranged in two fluidic passageways. Each sub-stack contains 100 cell pairs, so the total number of cell pairs per passageway is 200. The first device has a manifold cross-section as shown in FIG. 23A and the second device has circular profile protrusions inserted into a manifold with the same cross-section as shown in FIG. 23B .

[0190] FIG. 24A The pressure distribution through the base example module is shown. The pressure increases gradually from top to bottom in each passageway, which corresponds to the similar velocity profile through the stack. FIG. 24B How the pressure field is manipulated using protrusions in the manifold is demonstrated. This example of curved inserts shows the desired parabolic pressure field, with the highest pressure at the top and bottom of the passageway, and the lowest pressure in the middle of the passageway. This corresponds to the flow field shown in FIG. 25 . FIG. 26 Curves of the flow rate per cell pair into the active area per passageway in an ED device with and without the protrusions shown in FIG. 23B are shown, respectively. Without the protrusions, the flow rate per cell is lowest at the first cell in the passageway and increases as it passes through the passageway. The protrusions change the flow distribution so that the flow rate per cell is highest at the two ends of the manifold, where the current efficiency and current density in the active membrane area are expected to be the highest (see the curves of 200 cell pairs in FIG. 7 ). The higher flow rate will reduce the risk of current clipping and fouling in the end cells, and improve the overall salt removal in the passageway.

[0191] For manifolds with a uniform cross-sectional area, earlier described network models predicted that the bypass current would be highest midway through the path. Reducing the cross-sectional area would reduce the bypass current and improve current efficiency. FIG. 23B The protrusions in the ED device cause the cross-sectional area of ​​the inlet manifold to vary as it passes through each passage, and to be minimum at the midpoint of the manifold, which limits the bypass current.

[0192] To further reduce bypass current, additional inserts can be incorporated into the outlet manifold of each path. The shape of the insert can be optimized to occupy maximum volume in the outlet manifold while maintaining the desired flow profile. Similar to the inlet insert, setting up the ED device with an insert that creates a small cross-sectional area at the midpoint of the outlet manifold will significantly reduce current bypass. The geometry of the inlet or outlet manifold insert can include wedges, blades, baffles, ridges, or combinations thereof. Orifices or slots can also be incorporated to allow a portion of the flow to pass directly through, thereby reducing downstream vortices / eddies or dispersion. Various possible manifold outlet insert designs are as follows: FIG. 27 As shown.

[0193] The initial outlet manifold insert design was subjected to CFD analysis using the same prior CFD setup: two-stage, two sub-block / stage modules. FIG. 28 The first stage of a module with inlet and outlet manifold inserts is shown. The inlet manifold insert 2805 is arc-shaped, and the outlet manifold insert 2810 is a linear cone, with its widest portion at the top of the module and its narrowest portion at the bottom. As used herein, a "fluid guide" includes embodiments such as inlet manifold insert 2805 and outlet manifold insert 2810. The inlet insert is a smooth, continuous curve with a apex in the middle of the passage, narrowing the manifold to a 5 mm channel. The outlet insert is a straight cone that restricts the outlet manifold to a 4 mm channel at the top and provides an open channel at the bottom. The simulated flow rate was set to 12 gpm. FIG. 29 The mass flow rate curves (per cell pair) were plotted, showing that if the geometry of the outlet insert is smooth and flat, the flow profile remains essentially unchanged when the outlet insert is set.

[0194] The experiment was conducted using two cross-flow ED devices, each with two channels, and each channel having two sub-blocks. The first device has the following... FIG. 20B The manifold cross-section shown indicates that the second device has the following characteristics: FIG. 23B The circular protrusion shown is inserted into a manifold with the same cross-section.

[0195] The dilute and concentrate flow rates were in the range of 40-41 L / min, corresponding to an average velocity of ~2.5 cm / s in the compartments. The dilute and concentrate compartments were fed from separate tanks containing NaCl solutions. The initial concentration in the dilute feed tank was 556 mol / m 3 The initial concentration in the concentrate feed tank was 796 mol / m 3 The applied current was 10 A.

[0196] The product from the dilute compartment was recycled back to the dilute feed tank, and the waste from the concentrate compartment was recycled to the concentrate feed tank. During the experiment, the concentration of dissolved salt decreased in the dilute tank and increased in the concentrate tank.

[0197] FIG. 30 The process efficiency is shown as a function of the ratio of the average concentration in the concentrate to the average concentration in the dilute. This average concentration ratio increases as desalination progresses. In the device with the insert, the efficiency is about 10% higher, which is a result of improved flow distribution and the reduced cross-sectional area of the manifold in the middle of each pass.

[0198] Additional testing was performed in which outlet inserts were incorporated into the electrochemical separation device to improve flow distribution. The outlet inserts placed in the sub-blocks had sloped or tampered surfaces such that a turn of 90° in the absence of the insert was converted to a slope that directed the water flow to turn without creating turbulence at the corner of the turn. FIG. 31A and FIG. 31B A comparison between fluid flow with and without outlet inserts is shown. It was found that directing the water flow in the outlet manifold of the ED device with inserts helped to reduce the pressure drop within the module. However, the outlet inserts caused a restriction to the liquid flow through the outlet manifold, similar to obstructing the flow in a water pipe path by placing an object in the flow path of the pipe. The overall combined effect was that the pressure drop was actually slightly reduced compared to without the outlet inserts, which was an unexpected result. The use of the sloped or tapered outlet inserts also improved the process efficiency and reduced the energy consumption of the ED device. This data is shown in FIG. 32A and FIG. 32B .

[0199] Another aspect includes a fluid adapter for diverting a liquid flow from an external pipe having one geometric cross-sectional shape to an inlet manifold of an ED device having a different geometric cross-sectional shape. The fluid adapter includes a fluid conduit that includes at least one tapered portion, or in some embodiments, two tapered portions. Each tapered portion has a characteristic length for developing flow. In some embodiments, the two tapered portions do not overlap.

[0200] The liquid stream flowing into the dilution compartments of an ED device can be delivered via an external pipe to a fluid adapter, then distributed in parallel in all dilution compartments via an inlet manifold, as shown in FIG. 33 Similarly, the product from all dilution compartments can be collected in an outlet manifold and delivered through a fluid adapter to an external pipe. The liquid stream to and from the concentration compartments can be similarly arranged.

[0201] The transition of high velocity turbulent flow from an external pipe to an inlet manifold presents particular difficulties, as the cross section of the external pipe is typically circular, while the inlet manifold can have a cross section that is roughly circular, rectangular, triangular, or some other shape. FIG. 4 and FIG. 20A and FIG. 20B shows an inlet manifold that is roughly triangular. Therefore, it is common to provide a fluid adapter with specialized flow directing features.

[0202] In the isometric view of FIG. 34A , FIG. 34B the partially transparent view of FIG. 34C , FIG. 34D the top down view of FIG. 34C , and the bottom up view of FIG. 34D , one example of a fluid adapter is shown that provides a transition from a circular cross section to a roughly triangular cross section. The inlet cross section of this design is circular ( FIG. 34E ), while the outlet cross section is roughly triangular ( FIG. 34E ). Internally, the flow diameter is reduced over a first characteristic length ( FIG. 34F , LI) via a steep angled taper on a first axis ( FIG. 34F , D1-D2). It is then allowed to expand and develop over a second characteristic length ( , L2) via a wide angled taper that overlaps the first taper on a second axis (

[0203] , D3-D4). FIGS. 35A-35D An improved design of a fluid adapter for embodiments of the ED devices disclosed herein is shown. The inlet cross section of this design is also circular, while the outlet is also roughly triangular. In this design, the flow is also reduced over a first axis ( FIG. 35C , D1-D2), however, the first characteristic length ( FIG. 35C , LI) is larger, and the taper is more gradual and elliptical than in the previous design shown in FIGS. 34A-34F . The flow is again allowed to expand and develop over a second axis ( FIG. 35D , D3-D4), and the second characteristic length of flow development ( FIG. 35D , L2) is again larger than in the previous design. In this design, the tapers do not overlap.

[0204] FIG. 36A and FIG. 36B The simulated results of the magnitude of the velocity of individual streamlines for uniform sprouting at the inlet port in the inlet manifold for the base design and the optimized design are shown, respectively. Due to the jetting effect, the inlet manifold velocity is significantly higher in the base design (left) than in the optimized design (right).

[0205] FIG. 37A and FIG. 37B The simulated results of the Z-velocity component of fluid flow through the central ZY plane and through the top, middle, and bottom ZX planes for the ED devices including the base design and the optimized design are shown, respectively. Comparing the distribution of Z-velocity, there is a greater variation in the ED device including the base fluidic adapter compared to the optimized design.

[0206] The aspects and embodiments disclosed herein are not limited to electrodialysis devices. All electrochemical separation devices can benefit from improved flow distribution. Electrochemical separation devices include, but are not limited to, electrodialysis, electrodialysis reversal, continuous deionization, continuous electrodeionization, electrodeionization, electrodialysis and electrocapacitive deionization. Other electrochemical devices that would benefit from improved flow distribution include liquid flow batteries, fuel cells, electrochlorination cells, and caustic-chlorine cells.

[0207] The phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. As used herein, the term "plurality" refers to two or more items or components. The terms "comprising," "including," "carrying," "having," "containing," and "involving," whether in the written description or the claims or both, are open-ended terms, i.e., meaning "including, but not limited to." Thus, use of such terms is meant to provide support for a claim term as being open-ended term. Accordingly, the use of such terms is not meant to limit the scope of a claim term to the read items or components. With respect to the claims, the transitional phrases "consisting of" and "consisting essentially of" are closed or semi-closed transitional phrases, respectively. The use of ordinal terms, such as "first," "second," "third," and the like in the claims to list a number of claim elements does not by itself connote any prioritization, precedence, or order of one claim element over another, or the temporal sequence of actions of a method, but rather merely makes a distinction among claim elements. The use of the terms "first" and "second" are used to identify a claim element as being distinct from another claim element with the same name (but for the use of the ordinal term) to distinguish claim elements.

Claims

1. An electrochemical separation apparatus comprising: a first electrode; a second electrode; a cell stack comprising alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode; an inlet manifold configured to introduce a fluid into one of the depletion compartments or the concentration compartments; an outlet manifold; characterized in that the electrochemical separation apparatus further comprises: a fluid flow director removably disposed within the inlet manifold and comprising a plurality of ramps to alter a flow path of a fluid introduced into the inlet manifold and direct the fluid into one of the depletion compartments or the concentration compartments, and a second fluid flow director removably disposed within the outlet manifold and comprising a plurality of ramps to alter a flow path of a fluid introduced into the outlet manifold via one of the depletion compartments or the concentration compartments; wherein the cell stack comprises a plurality of sub-blocks and the plurality of ramps direct the fluid into different respective ones of the plurality of sub-blocks; wherein the fluid flow director further comprises a plurality of conduits that are fluidically isolated from one another.

2. The apparatus of claim 1, wherein, Each of the plurality of conduits terminates at a respective one of the plurality of ramps.

3. The apparatus of claim 2, wherein, A sum of cross-sectional areas of the plurality of conduits is less than a cross-sectional area of the inlet manifold.

4. The apparatus of claim 3, wherein, The second fluid flow director is configured to at least partially block a bypass current through the outlet manifold.

5. The apparatus of claim 4, further comprising: a second cell stack defining alternating second depletion compartments and second concentration compartments disposed between the cell stack and the second electrode; a second inlet manifold aligned with the outlet manifold and configured to introduce a fluid from the outlet manifold into one of the second depletion compartments or the second concentration compartments; a third fluid flow director disposed within the second inlet manifold, the third fluid flow director comprising a plurality of ramps to alter a flow path of a fluid introduced into the second inlet manifold and direct the fluid into one of the second depletion compartments or the second concentration compartments; a second outlet manifold disposed on an opposite side of the second cell stack from the second inlet manifold; and a baffle fluidically separating the inlet manifold from the second outlet manifold.

6. An electrochemical separation apparatus comprising: a first electrode; a second electrode; a cell stack comprising alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode; an inlet manifold configured to introduce a fluid into one of the depletion compartments or the concentration compartments; an outlet manifold; characterized in that the electrochemical separation apparatus further comprises: a fluid flow director removably disposed within the inlet manifold and comprising a plurality of ramps to alter a flow path of a fluid introduced into the inlet manifold and direct the fluid into one of the depletion compartments or the concentration compartments, and a second fluid flow director removably disposed within the outlet manifold and comprising a plurality of ramps to alter a flow path of a fluid introduced into the outlet manifold via one of the depletion compartments or the concentration compartments; ​ wherein the cell stack includes a plurality of sub-blocks and the fluidic flow director includes a plurality of baffles arranged to isolate flow of fluid into each of the plurality of sub-blocks from flow of fluid into other ones of the plurality of sub-blocks.

7. The apparatus of claim 6, wherein, The fluidic flow director further includes a concentric fluidic conduit.

8. An electrochemical separation apparatus comprising: a first electrode; a second electrode; a cell stack including alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode; an inlet manifold configured to introduce fluid into one of the depletion compartments or the concentration compartments; an outlet manifold; characterized in that the electrochemical separation apparatus further comprises: a fluidic flow director removably disposed within the inlet manifold and including a plurality of ramps to alter a flow path of fluid introduced into the inlet manifold and direct the fluid into one of the depletion compartments or the concentration compartments, and a second fluidic flow director removably disposed within the outlet manifold and including a plurality of ramps to alter a flow path of fluid introduced into the outlet manifold via one of the depletion compartments or the concentration compartments; wherein the fluidic flow director includes curved protrusions extending inward from walls of the inlet manifold toward the cell stack.

9. The apparatus of claim 8, wherein, The fluidic flow director reduces a cross-sectional area of the inlet manifold by a first amount at an end of the inlet manifold and by a second amount greater than the first amount at a midpoint along a length of the inlet manifold.

10. The apparatus of claim 9, wherein, The fluidic flow director is configured to reduce a fluid flow rate through compartments in a central region of the cell stack.

11. An electrochemical separation apparatus comprising: a first electrode; a second electrode; a cell stack including alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode; an inlet manifold configured to introduce fluid into one of the depletion compartments or the concentration compartments; an outlet manifold; characterized in that the electrochemical separation apparatus further comprises: a fluidic flow director removably disposed within the inlet manifold and including a plurality of ramps to alter a flow path of fluid introduced into the inlet manifold and direct the fluid into one of the depletion compartments or the concentration compartments, and a second fluidic flow director removably disposed within the outlet manifold and including a plurality of ramps to alter a flow path of fluid introduced into the outlet manifold via one of the depletion compartments or the concentration compartments; wherein the second fluidic flow director has a cross-sectional area that decreases along a flow path through the outlet manifold.

12. The apparatus of claim 11, wherein, The second fluidic flow director is configured to reduce a pressure drop of fluid through the apparatus.

13. An electrochemical separation apparatus comprising: a first electrode; a second electrode; a cell stack including alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode; an inlet manifold configured to introduce fluid into one of the depletion compartments or the concentration compartments; an outlet manifold; characterized in that the electrochemical separation apparatus further comprises: a fluid flow director removably disposed within the inlet manifold and comprising a plurality of ramps to alter a flow path of fluid introduced into the inlet manifold and direct the fluid into one of the depletion compartments or the concentration compartments, a second fluid flow director removably disposed within the outlet manifold and comprising a plurality of ramps to alter a flow path of fluid introduced into the outlet manifold via one of the depletion compartments or the concentration compartments; and a recirculation line configured to direct a concentrated liquid that has passed through the concentration compartment back into the concentration compartment.

14. An electrochemical separation apparatus comprising: a first electrode; a second electrode; a cell stack comprising alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode; an inlet manifold configured to introduce fluid into one of the depletion compartments or the concentration compartments; an outlet manifold; characterized in that the electrochemical separation apparatus further comprises: a fluid flow director removably disposed within the inlet manifold and comprising a plurality of ramps to alter a flow path of fluid introduced into the inlet manifold and direct the fluid into one of the depletion compartments or the concentration compartments, and a second fluid flow director removably disposed within the outlet manifold and comprising a plurality of ramps to alter a flow path of fluid introduced into the outlet manifold via one of the depletion compartments or the concentration compartments; wherein the inlet manifold is divided into fluidically isolated conduits configured to direct predetermined amounts of fluid to different portions of the cell stack.

15. The apparatus of claim 14, wherein, The fluidically isolated conduits have cross-sectional areas selected so that the fluid flow rate through compartments in a central region of the cell stack is less than the fluid flow rate through compartments in upper and lower regions of the cell stack.

16. The apparatus of claim 14, wherein, The fluidically isolated conduits have cross-sectional areas selected so that the fluid flow rate through compartments in an upper region of the cell stack is substantially equal to the fluid flow rate through compartments in a lower region of the cell stack.

17. A method of increasing current efficiency in an electrochemical separation device, the electrochemical separation device comprising a cell stack defining alternating depletion compartments and concentration compartments disposed between a first electrode and a second electrode, a fluid flow path through the depletion compartments being perpendicular to a fluid flow path through the concentration compartments, the method comprising: removably inserting a fluid flow director into an inlet manifold of the device, the fluid flow director comprising a plurality of ramps to alter a flow path of fluid introduced into the inlet manifold and direct the fluid into one of a plurality of depletion compartments or a plurality of concentration compartments, and at least partially block a bypass current through the inlet manifold.

18. The method of claim 17, further comprising increasing uniformity of fluid flow through the cell stack by installing a fluid adapter on an inlet of the inlet manifold, the fluid adapter comprising a conduit having a first portion with an inward taper in which a width of the conduit decreases in a first axis and a second portion with an outward taper in which the width of the conduit increases in a second axis, the first portion and the second portion not overlapping.

19. The method of claim 18, further comprising reducing pressure drop through the device by installing a tapered fluidic diffuser in an outlet manifold of the device.

20. The method of claim 18, further comprising installing a second fluidic diffuser in an outlet manifold of the device, the second fluidic diffuser having a curved surface that narrows a flow path through the outlet manifold by a first amount at a midpoint along a length of the outlet manifold and narrows the flow path through the outlet manifold by a second amount that is less than the first amount near an end of the outlet manifold.

21. An electrochemical membrane device, comprising: a first electrode; a second electrode; a cell stack comprising alternating depletion compartments and concentration compartments disposed between the first electrode and the second electrode; an ion-selective membrane separating the depletion compartments from the concentration compartments; an inlet manifold configured to introduce a fluid into one of the depletion compartments or the concentration compartments; an outlet manifold; wherein the electrochemical membrane device further comprises: a fluidic diffuser removably disposed within the inlet manifold and comprising a plurality of ramps to alter a flow path of a fluid introduced into the inlet manifold and direct the fluid into the one of the depletion compartments or the concentration compartments, and a second fluidic diffuser removably disposed within the outlet manifold and comprising a plurality of ramps to alter a flow path of a fluid introduced into the outlet manifold via the one of the depletion compartments or the concentration compartments.

22. The apparatus of claim 21, wherein, The device is an electrodialysis device for purifying a fluid using an electric field.

23. The apparatus of claim 21, wherein, The device is a reverse electrodialysis device for generating electrical energy from two or more fluid streams having different ion concentrations. The device is an electrodialysis device for purifying a fluid using an electric field. The device is a reverse electrodialysis device for generating electrical energy from two or more fluid streams having different ion concentrations.

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