Spiral electrochemical reactor

Abstract

A support structure for electrodes of a spiral electrochemical reactor comprises a manifold configured to retain a pair of parallel sheet electrodes rolled in a spiral and provide an axial flow of electrolyte between the sheets.

Description

[0001] Spiral Electrochemical Reactor

[0002]

[0001] Government Support Clause

[0003]

[0002] This invention was made with government support under Grant Number DE-AC02- 05CH11231 awarded by the United States Department of Energy, and under Grant Number DE- FOA-0001905 awarded by the National Alliance for Water Innovation. The government has certain rights in the invention.

[0004]

[0001] Introduction

[0005]

[0002] Many applications require compact electrochemical reactors with sacrificial electrodes. A common example is Iron (Fe) anode plates used in iron electro-coagulation (also referred as "FeEC"). The anodes dissolve into water releasing Fe ions that can oxidize to Fe+++ and serve as coagulant, co-precipitatant, or adsorbent. A common configuration is inter-digited sheets of iron, alternately serving as anodes and cathode. However, this configuration takes up too much space. Another previously disclosed configuration is two parallel sheets of iron, separated by an insulating mesh, rolled up together to form a tubular reactor (e.g. Gadgil US20220162094;

[0006] Heiss, US20090008269). However, in this configuration the mesh rapidly clogs up with iron oxide precipitates, and progressively impedes the flow of the electrolyte.

[0007]

[0003] Relevant Literature includes: Gadgil US20220162094; Heiss, US20090008269.

[0008]

[0004] Summary of the Invention

[0009]

[0005] In aspects and embodiments the invention provides:

[0010]

[0006] 1 . A support structure device for electrodes of a spiral electrochemical reactor, comprising a manifold configured to retain a pair of parallel sheet electrodes rolled in a spiral and provide an axial flow of electrolyte between the sheets, and without a cloggable mesh or perforated sheet between the electrodes.

[0011]

[0007] 2. A spiral electrochemical reactor comprising a support structure herein retaining a pair of parallel sheet electrodes rolled in a spiral and an axial flow of electrolyte between the sheets, preferably a pair of matching support structures herein, one at each of the bottom and top of spiral electrodes, preferably 3D printed.

[0012]

[0008] 3. A method of electrochemistry comprising use of an electrochemical reactor substantially as disclosed herein, preferably providing for high flow treatment with an in-line reactor.

[0013]

[0009] 4. A method of iron-electrocoagulation comprising use of an electrochemical reactor substantially as disclosed herein, preferably providing for high flow treatment with an in-line

[0014] 1 B25-068-2WO reactor, preferably for removal of a contaminant, such as arsenic or hexavalent chromium, from water.

[0015]

[0010] 5. A device or reactor or method herein, wherein the electrodes comprise a metal, preferably selected from iron, aluminum and magnesium (e.g. Devlin et al., J Hazard Mater, . 2019 Apr 15:368:862-868, Mechelhoff, et al., Chemical Engineering Science, 95, 2013, p. 301- 312, Cornejo, et al, Chemical Engineering Journal, 450, Part 3, 2022, 138222).

[0016]

[0011] 6. A device or reactor or method herein, wherein the electrode sheets are retained in corresponding parallel spiral grooves of the manifold, particularly wherein the grooves are configured to provide increased mechanical stability for the electrodes, such as from vibration induced by turbulence in the fluid electrolyte, wherein groove depth typically ranges from 100 to 0.5 mm, more preferably 50 to 5 mm.

[0017]

[0012] 7. A device or reactor or method herein, wherein the parallel sheet electrodes are spaced apart (inter-electrode distance) from 0.5 to 30 mm, more preferably from 1 to 15 mm, or from 2 to 10 mm.

[0018]

[0013] 8. A device or reactor or method herein, wherein residence time of electrolyte inside the reactor ranges from 1 second to 20 minutes, preferably 10 to 300 seconds, or 20 to 120 seconds.

[0014] The invention encompasses all combinations of the particular embodiments recited herein, as if each combination had been laboriously recited.

[0019]

[0015] Brief Description of the Drawings

[0020]

[0016] Fig. 1. FOX Reactor top-cap.

[0021]

[0017] Fig. 2. Spiral electrode support structure with a plurality of openings.

[0022]

[0018] Fig. 3. Bottom end of the FOX reactor, which also functions as the manifold for incoming water.

[0023]

[0019] Fig. 4. Main body, or the cylindrical wall, of the reactor.

[0024]

[0020] Fig. 5. Electrode spacers used to maintain separation between the two spiral electrodes at the top end of the reactor.

[0025]

[0021] Fig. 6. Simple rectangular geometry of spacers enables easy insertion and removal while ensuring reliable mechanical alignment of the spiral electrodes.

[0026]

[0022] Fig. 7. Two separate 3D-printed FOX reactors operating in parallel during testing.

[0027]

[0023] Fig. 8. Spiral electrode assembly constructed from low carbon steel shim material.

[0028]

[0024] Description of Particular Embodiments of the Invention

[0029]

[0025] Unless contraindicated or noted otherwise, in these descriptions and throughout this specification, the terms “a” and “an" mean one or more, the term “or" means and / or. It is

[0030] 2 B25-068-2WO understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. All publications, patents, and patent applications cited herein, including citations therein, are hereby incorporated by reference in their entirety for all purposes.

[0026] Spirally wound electrochemical reactors are compact, can be operated in-line, and can be easily replaced as they wear out. When voltages must be kept low for improved operational safety, inter-electrode distances must be small to achieve high current densities required for high dosing during high flow rates. Electrode separation achieved with large spacing is therefore unattractive. Electrodes insulated with a porous insulating mesh between lead to rapid clogging from a build of insoluble reaction products that should be flushed out with the fluid flow under normal conditions. Another method, mounting a plurality of insulating (e.g., plastic) studs or spacers on the electrode surfaces, is laborious, and wastes precious electrode surface area that is covered with the insulating spacers or studs. And can also lead to clogging as does the insulating mesh used as a spacer.

[0031]

[0027] This invention solves the problem posed by clogging of tightly wound spiral electrochemical reactors with small inter-electrode spacing, and allows for a modular design. The invention provides for unclogged long term operation of spirally wound reactors, such as FeEC reactors. This is desirable because it saves space, allows for high flow rates and high current densities with long term operation until the anode plate wears out from dissolution, at which time the reactor can be replaced with a fresh reactor.

[0032]

[0028] The invention is suitable for any application where iron-electrocoagulation is needed for high flow treatment with an in-line reactor, such as removal of arsenic (or other, such as hexavalent chromium) contamination from water.

[0033]

[0029] The invention design avoids a cloggable mesh or perforated sheet between the electrodes. The spacing between the sheets of electrodes is maintained by locking the sheets each in their own spiral groove in one or two end plates. The curvature of the electrodes provides sufficient stiffness such that they do not bend and touch each other.

[0034]

[0030] The invention is generally applicable in the field of spirally wound electrochemical reactors, including those that can be used for iron electrocoagulation. It allows the reactors to be reliable products that can be used in-line, and rapidly switched out when the reactant (e.g., an electrode participating in the reaction) is spent out.

[0035]

[0031] The invention is used support narrowly spaced spiral electrodes. One embodiment integrates a manifold with the base-plate of the deep-grooved electrode support system, and

[0036] 3 B25-068-2WO similarly at the exit of the flow. In embodiments there are only two parts that are 3-D printed, one at each end of the reactor.

[0037]

[0032] For manufacturing the support, any non-conducting water-impervious material may be used, that is safe for the intended application. Preferred classes of materials are those that can be (1) used with 3-D printing machines, or (2) formed with plastic molding equipment.

[0038]

[0033] A prototype embodiment comprises a bottom piece manifold with an inlet for water. The top surface of the manifold has a closely spaced double-spiral deep grooves at its top surface. The space between the grooves has holes that allow water from the bottom manifold to exit the manifold and enter the space between the grooves. A pair of parallel sheets of the electrode material are each rolled in a spiral and inserted in their own groove (the grooves act as their separators and hold them apart. Water (electrolyte) enters the space between the electrodes via the holes in the top cap on the manifold, and flows upwards. At the top end a similar arrangement may be used support the electrodes and keep them spaced closely apart. The full arrangement thus supports two closely spaced spiral shaped electrodes with the electrolyte flowing axially between them.

[0039]

[0034] Example: Iron Electrocoagulation with External Oxidizer (FOX) Electrode Support.

[0040]

[0035] This example describes a single instantiation of a disk-supported spiral-electrode design. Fig. 1 shows the FOX reactor top-cap in two perspectives. The top-cap is designed to fit a 6-inch threaded cylindrical wall and features two threaded side outlets for attaching standard PVC fittings. The upper opening of the Top-Cap is open to the atmosphere and allows access for electrical leads. A suitable cover with penetrations (not shown) may be added to the upper opening of the Top-Cap.

[0041]

[0036] Internally, the top-cap includes a threaded bottom lip, visible in the right-panel, which allows it to securely twist onto the cylindrical reactor body. The clean cylindrical geometry provides a watertight seal between the cylindrical walls and the top-cap, when attached, while the side ports allow flow of water, and / or wires for instrumentation as needed.

[0042]

[0037] Fig. 2 shows the 3D-printed spiral support structure that fits the bottom end of the cylindrical body of the reactor (Fig. 4), and fits above the Bottom End of the reactor (see Fig. 3). In this instantiation, the horizontal disk of the structure has 104 circular openings, each with a diameter of 0.10 inches, allowing water to pass upward from the manifold chamber. Together, these openings provide a total flow cross-sectional area of 0.817 square inches.

[0043]

[0038] Two concentric spiral grooves, which serve as slots for seating the two spiral-shaped electrodes, cover the surface of the disk. These grooves do not penetrate through the disk; they stop short of the bottom surface of the disk (see Fig. 2, top right panel), and thus provide

[0044] 4 B25-068-2WO mechanical support for the electrodes and prevent unwanted bypass flow through the groove paths. Each groove is 0.40 inches deep, measured from its starting point on the top surface of the disk.

[0045]

[0039] The central vertical rod shown is a separate component. It is threaded so it can be twisted securely in place, helping avoid dead zones (i.e., stagnant pockets of water) inside the reactor during operation (see Fig. 2, top left panel and bottom left panel). The diameter of this inner cylinder of this assembly is adjustable to suit electrode dimensions.

[0046]

[0040] The inner surface of the wall of this structure is fully threaded. The threads on the upper part of the wall, that extend above the disk, allow the cylindrical wall of the main reactor to twist on securely, forming a tight, sealed mechanical engagement between the spiral electrode support structure and the cylindrical reactor body (see Fig. 2, bottom rt panel). The threads on the lower part of the wall, that extend below the disk, are seen on the lower right panel of Fig. 2. These threads allow a secure seal with the threads on exterior walls of the manifold shown in Fig. 3.

[0047]

[0041] Fig. 3 shows the bottom end of the FOX reactor, which also functions as the manifold for incoming water. The side inlet — a barbed connection that can alternatively be threaded — has an inner diameter of 0.34 inches and allows water to enter the manifold from an external feed line. Once water enters the manifold, it moves upward through the openings (holes) in the spiral- support-disk (see Fig. 2). Water passes through the 104 distributed openings in the disk, providing uniform upward flow into the electrode region.

[0048]

[0042] Fig. 4 shows the main body, or the cylindrical wall, of the reactor. It connects at one end with the Spiral Electrode Support Structure (sec Fig. 2). It connects at the other end to the FOX Reactor Top-Cap (see Fig. 1. It has threading on its external surface, near both ends of the cylinder. These threads match the threads on the inner walls of the Bottom Cap and l op Cap, so it fits securely with a stable sealed interface. In this instance, the wall is 9 inches tall.

[0049]

[0043] Fig. 5 is a digital photograph showing the electrode spacers used to maintain separation between the two spiral electrodes at the top end of the reactor. Each spacer is 3 cm (1.20 inches) long and 0.76 cm (0.30 inches) wide, with a 1 cm (0.40-inch) deep groove designed to accommodate the electrode plate thickness.

[0050]

[0044] These spacers are positioned in a distributed pattern around the circumference of the spiral assembly. Their primary function is to prevent physical contact between the anode and cathode, thereby eliminating the risk of electrical shorting. By supporting the spirals from the top end, the spacers maintain consistent inter-electrode spacing during operation, even as the plates gradually dissolve in the electrochemical process.

[0051]

[0045] Fig. 6 shows that the simple rectangular geometry enables easy insertion and removal while ensuring reliable mechanical alignment of the spiral electrodes.

[0052] 5 B25-068-2WO

[0046] Fig. 7. is a digital photograph showing two separate 3D-printed FOX reactors operating in parallel during testing. The left reactor has a transparent acrylic cylindrical housing, and the right reactor has its cylindrical housing 3-D printed from opaque gray plastic material.

[0053]

[0047] The transparent cylindrical wall of the left reactor allows direct observations of internal processes such as electrode dissolution and flow distribution. This clear-wall design was used to validate hydraulic behavior and confirm that the spiral electrodes remained properly supported during operation.

[0054]

[0048] The reactor on the right uses a fully 3D-printed opaque wall, demonstrating the final configuration intended for field use. Both reactors share the same internal geometry — manifold, spiral support structure, and threaded interfaces — but differ only in housing material to facilitate both research observation and test the performance in practical deployment.

[0055]

[0049] Fig. 8 is a digital image showing a spiral electrode assembly constructed from 1010 low carbon steel shim material with a thickness of 0.007 inches. The steel sheet is rolled into a spiral, and inserted into the 3D-printed support structure, where the grooves and top-end spacers maintain uniform separation between electrodes.

[0056]

[0050] Alternative electrode materials and thicknesses can also be used. In addition to 1010 steel, 1008 low carbon steel is compatible with the FOX design. The structure accommodates a range of steel thicknesses — including 0.004 in, 0.007 in, 0.010 in, and 0.012 in — allowing tailoring of performance, dissolution rate, and structural rigidity for different operating conditions.

[0057]

[0051] Field Testing and Validation

[0058]

[0052] The four major components of the assembly — the bottom end, spiral electrode support structure, the wall, and the top cap -were 3D-printed. Then spiral electrodes were installed inside a cylindrical mid-section (see Fig. 4). The full assembly was operated continuously in a two-month field deployment. During this period, the system experienced real groundwater conditions, including variable flow rates, dissolution of the iron electrodes, and accumulation of some of the solids from iron dissolution, in parts of the reactor assembly. The spiral electrodes remained securely seated in the non-penetrating grooves, and the threaded interfaces between all components held their seal without leakage. The assembly did not get clogged with the small amounts of iron oxides that accumulated. Over the course of testing, the electrodes were gradually consumed as designed (“ate through the plate”), demonstrating that the design effectively supported electrochemical reactions while maintaining structural stability. The successful field test confirmed that the geometry, hole distribution, and threaded connections all perform reliably in real operating environments.

[0059] 6 B25-068-2WO

Claims

CLAIMS1 . A support structure device for electrodes of a spiral electrochemical reactor, comprising a manifold configured to retain a pair of parallel sheet electrodes rolled in a spiral and provide an axial flow of electrolyte between the sheets, and without a cloggable mesh or perforated sheet between the electrodes.

2. A device according to claim 1, wherein the device is 3D printed.

3. A device according to claim 1, substantially as shown in Figs. 1 and 2.

4. A spiral electrochemical reactor comprising a device according to claim 1, and comprising and retaining a pair of parallel sheet electrodes rolled in a spiral and an axial flow of electrolyte between the sheets.

5. A spiral electrochemical reactor comprising a first device according to claim 1 , and comprising and retaining a pair of parallel sheet electrodes rolled in a spiral and an axial flow of electrolyte between the sheets, and a second device according to claim 1, to form a pair of matching support structure devices, one at each of the bottom and top of spiral electrodes.

6. A reactor according to claim 5, substantially as shown in Figs. 5, 7 and 8.

7. A reactor according to claim 4, 5 or 6, wherein the bottom end, spiral electrode support structure, the wall, and the top cap are each 3D printed.

8. A reactor according to claim 4, 5 or 6, wherein the electrodes comprise a metal, preferably selected from iron, aluminum and magnesium.

9. A reactor according to claim 4, 5 or 6, wherein the electrode sheets are retained in corresponding parallel spiral grooves of the manifold,10. A reactor according to claim 4, 5 or 6, wherein the electrode sheets are retained in corresponding parallel spiral grooves of the manifold, wherein the grooves are configured to provide increased mechanical stability for the electrodes, such as from vibration induced by turbulence in the fluid electrolyte.7 B25-068-2WO11. A reactor according to claim 4, 5 or 6, wherein the electrode sheets are retained in corresponding parallel spiral grooves of the manifold, wherein the grooves are configured to provide increased mechanical stability for the electrodes, such as from vibration induced by turbulence in the fluid electrolyte, wherein groove depth ranges from 100 to 0.5 mm, preferably 50 to 5 mm.

12. A reactor according to claim 4, 5 or 6, wherein the parallel sheet electrodes are spaced apart (inter-electrode distance) from 0.5 to 30 mm, preferably from 1 to 15 mm, or from 2 to 10 mm.

13. A reactor according to claim 4, 5 or 6, wherein residence time of electrolyte inside the reactor ranges from 1 second to 20 minutes, preferably 10 to 300 seconds, or 20 to 120 seconds.

14. A reactor according to claim 4, 5 or 6, wherein the bottom end, spiral electrode support structure, the wall, and the top cap are each 3D printed.

15. A method of electrochemistry comprising use of an electrochemical reactor of claim 4, 5 or 6, providing for high flow treatment with an in-line reactor.

16. A method of iron-electrocoagulation comprising use of an electrochemical reactor of claim 4, 5 or 6, providing for high flow treatment with an in-line reactor, for removal of a contaminant from water.

17. A method of iron-electrocoagulation comprising use of an electrochemical reactor of claim 4, 5 or 6, providing for high flow treatment with an in-line reactor, for removal of a contaminant selected from arsenic and hexavalent chromium, from water.8 B25-068-2WO

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