High pressure hydrogen production system and method of using same

Abstract

A high pressure electrolyte system, having at least one electrolysis cell having at least a first electrode and a second electrode, and in which at least one of the electrodes produces hydrogen at a pressure of greater than 30 bar, is presented. The at least first and the at least second electrode may be separated by at least one non-electrode electrolyte sweep layer. A liquid electrolyte may recirculate from the electrolyte sweep area to a gas-liquid separator, and hydrogen may be evolved from the recirculating electrolyte sweep area within the gas-liquid separator. Gases produced within the system may be at least partially recycled through the system for further processing.

Description

APPLICATION FOR UNITED STATES LETTERS PATENTFOR AHIGH-PRESSURE HYDROGEN PRODUCTION SYSTEM AND METHOD OF USINGSAMESpecification: 23 Total PagesClaims: 16 Total Claims including 3 (1, 5, 11) Independent and 13 Dependent Claims5 Figures in 9 Drawing SheetsInventors:Paul H. Matter, a citizen of the U.S.A.Minette Ocampo Quimba, a citizen of the U.S.A.Travis M. Hery, a citizen of the U.S.A.Christopher T. Holt, a citizen of the U.S.A.Attorney: Docket No. 18471-36Michael J GallagherLUPER NEIDENTHAL & LOGAN 1160 Dublin Road, Suite 400 Columbus, OH 43215PH. And FAX: (614) 221-7663 Cust. No. 155,017TITLE

[0001] High-Pressure Hydrogen Production System and Method of Using SameSTATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with government support under NASA Contract 80LARC21C0006 and Department of Energy Contract DE-AR0001357. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present disclosure relates generally to an electrochemical hydrogen production system and a method of using the same.CROSS-REFERENCE TO RELATED APPLICATIONS

[0004] This application claims the benefit of United State Provisional Patent Application 63521742; filed June 19, 2023.BACKGROUND OF THE INVENTION

[0005] Currently, two technologies are used commercially for most water electrolysis applications. Alkaline electrolyzers are an established technology that relies on two electrodes submerged in a liquid electrolyte. These electrodes are typically separated by an electrically insulative porous layer, called the separator. Through application of voltage, hydrogen andoxygen are evolved from the cathode and anode, respectively. Due to the permeability of the separator, the hydrogen gas cannot be pressurized substantially through electrochemical means. Small differences in pressure between the two sides of the cell can cause catastrophic cell failures due to gas mixing. A mechanical compressor is typically used for hydrogen compression, requiring an additional system component that is exceedingly expensive for many scales and applications, and has low efficiency.

[0006] The second common method for water electrolysis is a proton exchange membrane (PEM) electrolyzer. This technology uses a gas-impermeable polymer membrane as the electrolyte. Water vapor or liquid water is fed to at least one of the electrodes. The gases can be compressed electrochemically with a PEM electrolyzer, and the cells can operate with pressure differences. However, thick membranes, which reduce efficiency, are required for higher pressure operation.

[0007] A second drawback of PEM electrolyzers is the cost of the components. The acidic electrolyte and electrolysis operating voltages necessitate the selection of expensive components for long-term stability. Platinum and Iridium may be used as electrode catalysts. Additionally, electrode current collectors must be fabricated of corrosion-resistant materials. Consequently, PEM electrolysis systems are often too expensive for wide-scale commercial adoption for industrial scale applications. Further, the porous transport layer components used in PEM electrolyzers, such as titanium frits, are flammable in oxygen at elevated pressure, making it unsafe to operate at elevated oxygen pressures

[0008] With the development of polymer membranes, known as Anion ExchangeMembranes (AEMs), that conduct hydroxide ions and other anions, low-cost cells that can produce pressurized hydrogen have become possible. However, hydrocarbon-based AEMs havechallenges with remaining conductive if operated in the absence of liquid water. Further, without liquid electrolyte present, ionomers in the electrode layer are required to introduce ion conduction beyond the 2-dimensional el ectrolyte / el ectrode interface, a necessity for obtaining high areal current density.

[0009] The primary challenge with operation of water electrolysis at high pressure is that hydrogen can cross through electrolyte membranes and liquid electrolyte via diffusion due to partial pressure differences or can pass through liquid electrolyte via convection due to pressure differences. This hydrogen crossover can cause a loss in hydrogen production efficiency, contaminates the oxygen with hydrogen, and can lead to dangerous gas mixtures. Those skilled in the art would appreciate that crossover is typically addressed by increasing the thickness of the electrolyte membrane or the thickness and tortuosity of the liquid electrolyte separator layer. These solutions increase the resistance of an electrolysis cell, thus decreasing efficiency and performance. At pressures above approximately 30 bar hydrogen, the membranes of PEM electrolyzers become so thick that further pressure increase is impractical or disadvantageous in many commercial applications. Liquid alkaline electrolyzers can theoretically operate at higher pressures with less crossover, as potassium hydroxide solutions are known to have low hydrogen solubility relative to their high ionic conductivity, but careful pressure balance is required, and such systems are not practical given the risk of hydrogen and oxygen mixing.

[0010] In electrolyzers that produce gases directly at high pressure, it also becomes necessary to detect and remove contaminants at high pressure. Conventional flammability sensors are not rated for operation at high pressure. To remove hydrogen from oxygen, or remove oxygen from hydrogen, at low pressures, a recombiner is often used. A recombiner can also detect contamination based on the amount of heat produced. Recombiners typically consistof a combustion catalyst paired with temperature control and thermocouples. However, use of a recombiner at high pressure can be problematic for several reasons. First, during cell failures, flammable mixtures can be sent to the recombiner. The flammable mixture can increase pressure in the recombiner by 10X or more if combustion occurs. Given the already high operating pressure, a 10X increase would exceed pressure limits for existing designs. Second, flammable mixtures can lead to flames propagating outside of the recombiner, particularly at higher pressures. Commercial flame arrestors rated for above 30 bar oxygen and / or hydrogen operation are not readily available. Finally, at high pressure it is important to use the recombiner as a detection method given the lack of commercial high-pressure gas sensing options; however, volumetric flow rates are much lower at high pressure, making heat detection more challenging.

[0011] In situations where high-pressure hydrogen is not required, it may be advantageous to use a thin electrolyte layer to increase performance. However, even at low pressure the thickness of the electrolyte layer is limited by hydrogen crossover. One solution, in applications where only low-pressure hydrogen is required and oxygen is not valuable, is to dilute the product oxygen with air to avoid dangerous mixtures (USP Appl 20220364246A1). This solution works in some instances but is not practical for lower cost alkaline applications where carbon dioxide from air would neutralize the electrolyte. This approach also results in loss of crossover hydrogen, which is expelled with the oxygen / air mixture.

[0012] In the instant invention an electrolyzer is paired with a recirculation loop that provides protection from the formation of dangerous gas mixtures, thus forming a safe and efficient high-pressure hydrogen generation system. In one example, a liquid electrolyte loop is used as the recirculation loop. Liquid electrolyte is passed between the electrodes in the electrolysis cell and a gas / liquid separator using a pump. In this design an AEM can be used inseries with a liquid electrolyte sweep to prevent convective transport of hydrogen or oxygen.Examples of such cell designs have been described in prior art (US Patents 10,844,497 and 11,228,051 ). This liquid electrolyte sweeps crossover hydrogen and oxygen from the cell to minimize hydrogen contamination in the oxygen and oxygen contamination in the hydrogen, respectively. The removed hydrogen is evolved in a liquid / gas separator, where it can be captured or vented. If it is desirable to capture the hydrogen, it may be passed through a recombiner to remove oxygen contamination.

[0013] In another embodiment, a high pressure electrolyzer is paired with an oxygen recirculation loop that provides protection from the formation of dangerous mixtures. A portion of the product oxygen from the electrolyzer is recirculated with a blower through a recombiner. The recombiner removes hydrogen contamination from the recycled oxygen. The cleaned recycled oxygen is then passed back to either the entrance or exit of the electrolyzer oxygen manifold. The recycled oxygen mixes with newly produced product oxygen to ensure dilution of any crossover hydrogen to safe levels. The ratio of oxygen recycled is designed to optimize system efficiency while ensuring dangerous mixtures cannot be formed under possible operating conditions. Possible operating conditions can include changes in current, changes in pressure, and dynamic on / off operation.SUMMARY OF THE INVENTION

[0014] What is described in greater detail below, includes a high pressure electrolyte system, having at least one electrolysis cell having at least a first electrode and a second electrode, and in which at least one of the electrodes produces hydrogen at a pressure of greater than 30 bar. The at least first and the at least second electrode may be separated by at least onenon-electrode electrolyte sweep layer. A liquid electrolyte may recirculate from the electrolyte sweep area to a gas-liquid separator, and hydrogen may be evolved from the recirculating electrolyte sweep area within the gas-liquid separator.

[0015] The system may have at least one anion exchange membranes (AEM) that separates hydrogen and oxygen separation during gas evolution, and at least one anion exchange membrane (AEM) may separate at least one product gas and the liquid electrolyte sweep layer. Hydrogen evolved within the gas separation layer may be purified with a recombiner.

[0016] In another embodiment, a high pressure electrolysis system producing hydrogen at pressures of at least equal to or greater than 30 bar may be constructed, where at least a portion of an evolved oxygen product is recirculated through a recombiner to remove hydrogen contamination and recirculation of the portion of the purified product oxygen gas is blended with product oxygen. In other embodiments, hydrogen may be produced at pressures of at least equal to or greater than 70 bar, 100 bar, 250 bar, 350 bar, 500 bar, 900 bar, or possibly greater.

[0017] In yet another embodiment, an electrolysis system producing hydrogen at a pressure of at least equal to or greater than 2 bar may be constructed, including at least, an anion exchange membrane (AEM) separating evolved hydrogen and oxygen, wherein the AEM is equal to or less than 100 microns thick, and where a portion of oxygen product gas is recirculated through a recombiner to remove hydrogen contamination, and at least a portion of oxygen product gas is blended with the oxygen product gas. Such a system may be configured to produce hydrogen at a pressure of at least equal to or greater than 10 bar, 30 bar, or possibly more. In various embodiments, the anion exchange membrane (AEM) is equal to or less than 75 microns thick, equal to or less than 50 microns thick, or equal to or less than 25 microns thick.BRIEF DESCRIPTION OF THE ILLUSTRATIONS

[0018] Without limiting the scope of the High Pressure Hydrogen Production System and Method of Using Same as disclosed herein and referring now to the drawings and figures:

[0019] FIG. l(a-c) show an embodiment of a cell design that may be used in the instant invention;

[0020] FIG. 2(a-b) show a further embodiment of a cell design that may be used in the instant invention;

[0021] FIG. 3 shows an embodiment including a high-pressure recombiner;

[0022] FIG. 4 shows an embodiment with multi-layer electrolyte that includes a liquid electrolyte sweep layer; may be used to reduce crossover of hydrogen into the product oxygen; and

[0023] FIG. 5 shows an embodiment of an electrolysis system where oxygen is recycled through a recombiner.

[0024] These illustrations are provided to assist in the understanding of the exemplary embodiments of a high-pressure hydrogen production system, and a method for using the same, as described in more detail below, and should not be construed as unduly limiting the specification. In particular, the relative spacing, positioning, sizing and dimensions of the various elements illustrated in the drawings may not be drawn to scale and may have been exaggerated, reduced or otherwise modified for the purpose of improved clarity. Those of ordinary skill in the art will also appreciate that a range of alternative configurations have been omitted simply to improve the clarity and reduce the number of drawings.DETAILED DESCRIPTION OF THE INVENTIONExamples:Example 1 - Example of a Cell Design

[0025] Figures 1 and 2 show an embodiment of a cell design that may be used in the instant invention. This cell design consists of a series of layers that are stacked to form a cell (10). The first layer may be the hydrogen electrode endplate (100). In this embodiment the plate may be made of stainless steel. The hydrogen end plate (100) may contain hydrogen inlet (110) and outlet ports (120) and be attached to a tab or wire that supplies current. The endplate may also include bolt holes (15) to allow the cell or a series of cells to be bolted together.

[0026] In some instances, such as a water electrolysis cell, the hydrogen end plate (100) may only require a hydrogen outlet port (120). The next layer may be the first hydrogen frame / seal (200). In this embodiment the frame / seal is made of thin PTFE sheets. Seal layers could also be made of epoxy, rubber, polysulfone, other polymers, or a combination thereof. Voids in the seal extend to the hydrogen port(s) (210, 220) to allow gas in and / or out of the electrode. One skilled in the art would realize that in another embodiment, the ports (210, 220) could be co-extant with current collector mesh and flow field (250). This seal frames the hydrogen electrode current collector (250), and the hydrogen flow field. In an embodiment, the hydrogen electrode current collector (250) may be stainless steel mesh. In an embodiment the second hydrogen seal (300) frames a hydrogen electrode (201630053008). In an embodiment, the hydrogen electrode (350) may be porous carbon paper coated with a mixture of catalyst and AEM ionomer. A preferred catalyst for the hydrogen electrode (350) may be 50-wt% ruthenium supported by Vulcan carbon. The hydrogen-side AEM layer (400) may sit on top of the secondhydrogen seal (300) and the framed hydrogen electrode (350) layer. In an embodiment, the cathode / hydrogen electrode may be flooded with electrolyte, such as aqueous potassium hydroxide with 0.05 to 9 molarity. In another embodiment, the cathode may be effectively dry, such as less than 50% filled with liquid by volume.

[0027] The next layer may be the electrolyte sweep layer (500). The electrolyte sweep layer (500) consists of a thin separator frame / seal that frames a porous matrix (550). In one embodiment, the porous matrix may be nickel foam compressed to the thickness of the separator frame / seal. In another embodiment, the porous matrix may be channels within a polymer, metal shim, and / or mesh. In one embodiment, the separator seal also contains inlet and exit ports (510, 520) for aqueous electrolyte, preferably aqueous potassium hydroxide, sodium hydroxide, or other alkaline salt solution. Channels, such as an electrolyte inlet channel (530) and electrolyte outlet channel (540), in the electrolyte layer seal allow the electrolyte to flow into the bottom of the porous matrix (550) and out the top of the porous matrix (550) while sweeping crossover hydrogen from the cell. The oxygen-side AEM layer (600) sits on top of the electrolyte layer and the framed porous matrix layer. In another embodiment, the oxygen-side AEM layer (600) may include a porous separator layer, such as porous ceramic or porous polymer, to avoid contact between the AEM and high voltage oxygen electrode (750). In yet another embodiment, layer (600) may be only a separator, such as porous ceramic or porous polymer, and not an AEM. In one embodiment, layer (600) may also contain inlet and exit through ports (610, 620) for aqueous electrolyte.

[0028] Next, the first oxygen seal (700) sits on top of the oxygen-side AEM (600). This seal frames the oxygen electrode (750). The oxygen electrode (750) may be porous nickel foam coated with catalyst. A preferred catalyst for the oxygen electrode (750) may be a mixture ofnickel and other transition metals, including oxide and hydroxide phases. In one embodiment, layer (700) may also contain inlet and exit through ports (710, 720) for aqueous electrolyte.

[0029] In an embodiment a second oxygen seal (800) seals the oxygen electrode current collector (850). In this embodiment, the oxygen electrode current collector (850) may be stainless steel mesh. The oxygen-side seal may also contain through-ports (810, 820) for the electrolyte sweep. Voids in the second seal (800) extend to the oxygen inlet / outlet port(s) (830, 840) to allow gas in and / or out of the electrode. One skilled in the art would realize that electrolyte could separately be fed to the oxygen electrode to improve electrolysis performance using the oxygen inlet / outlet ports (830,840). One skilled in the art would realize that in another embodiment, the ports (830, 840) could be co-extant with current collector mesh and flow field (850). In an embodiment, the oxygen inlet port (830) could be used to feed recycled oxygen to the cell.

[0030] The final layer may be the oxygen end plate (900). The oxygen end plate (900) may contain oxygen inlet (930) and outlet (940) ports. In some instances, such as an electrolysis cell, electrolyte and / or oxygen may be fed to the oxygen inlet (930). The endplate (900) may also contain ports (910, 920) for a separate aqueous sweep electrolyte to enter and exit the cell, and a tab or wire for current collection. One skilled in the art could also appreciate how the design could be modified to enable a number or cell repeat units to be stacked in series. In such a design, the interior layers could use through-ports for the oxygen / electrolyte, hydrogen, and sweep electrolyte The oxygen and hydrogen ports would need to be offset in such an embodiment. Conductive interconnect plates could be used between cell repeat units to connect a plurality of cells in series to form a cell stack. To minimize crosstalk effects through the electrolyte between cells at the top and bottom of the series, a tortuous electrolyte flow pathwould be preferred. Isolation of conductive materials from electrolyte would be preferred, such as coating the interconnect electrolyte through-ports.

[0031] One skilled in the art could also envision a number of alternative electrolyte membrane designs. For example, an AEM could be mechanically supported by a porous layer or other mechanical support to stabilize a thin AEM. Further, in some uses for the cell design it may not be necessary to use two AEM layers per cell. One of the AEM layers could be replaced by a porous separator, such as a porous polypropylene.Example 2 - High pressure recombiner design

[0032] A recombiner is a reactor that combines hydrogen gas and oxygen gas to form water. Many high-pressure systems require a recombiner for safe operation. An embodiment of a high-pressure recombiner is shown in Figure 3. In a preferred embodiment, the recombiner contains a catalyst (1009) for combustion of hydrogen in oxygen or oxygen in hydrogen; the catalyst may be coated on a support structure (interior of 1004 and 1008), such as alumina media or metal foam. The catalyst may be contained in a housing comprised of high-pressure tubing and high-pressure gas fittings. In an embodiment, the high-pressure tubing and fittings are rated for pressures greater than 30 bar. In a preferred embodiment, the tubing and fittings are rated for pressures greater than 900 bar. In a preferred embodiment, the recombiner comprises a first catalyst zone (1004) that is heated. This zone ensures the catalyst remains dry and active, and thus the reaction initiates prior to a thermocouple (1007) in the gas stream. The zone is heated to a minimum sufficient temperature to ensure the gas and catalyst is dry. In a preferred embodiment, the zone is heated to 90°C. In use cases where the recombiner provides detection of gas contamination, a thermocouple (1007) is placed inside the reactor by means of a high pressure tee (1005) and a high pressure bored through union (1006). In alternative configurationsthe thermocouple (1007) may be attached to the outside of the reactor housing. The thermocouple (1007) detects if heat is released from combustion of gas in the recombiner. In a preferred embodiment, a second catalyst zone (1008) may be placed down-stream of the first catalyst zone (1004) and thermocouple (1007). This second catalyst zone (1008) removes any remaining gas contaminant and adds additional volume to the reactor that minimizes possible rapid pressure increase. In some embodiments, additional thermocouples (1007) and catalyst zones may be placed on the entrance, exit, and at additional locations on the reactor housing. These thermocouples (1007) determine if the catalyst in the preceding zone has deactivated. In such a scenario, more heat is released in the second zone than the first.

[0033] Finally, in a preferred embodiment, two nickel flame arrestors (frits) (1003) with pore size less than 10 microns, and preferably less than 1 micron are located in the recombiner; the frits (1003) may be made out of nickel or ceramic. One frit (1003) is placed on each end of the catalyst housing. These frits (1003) act as flame arrestors and ensure that flames cannot escape the recombiner catalyst zones if a flammable mixture is provided to the recombiner, either intentionally or during a system failure. These frits (1003) also ensure that catalyst remains in the reactor. The recombiner may be connected to high pressure tubing on the inlet and exit (1001), thus allowing gas to be fed through the reactor at high pressure. High pressure tube unions (1002) may connect the recombiner to the tubing.Example 3 - System with Electrolyte Sweep Layer

[0034] A cell design with multi-layer electrolyte that includes a liquid electrolyte sweep layer may be used to reduce crossover of hydrogen into the product oxygen. An embodiment of such a cell design is shown in Figure 4 from a cross-section perspective. In this embodiment, liquid electrolyte is fed by an electrolyte circulation pump (2014) via an electrolyte sweep layerinlet stream (2006) through an electrolyte sweep layer (2003) between a hydrogen-side AEM (2002) and an oxygen-side AEM or separator (2004), which are all located between the hydrogen (2001) and oxygen (2005) electrodes. The electrolyte removes crossover hydrogen before it reaches the oxygen electrode and exits the cell via the electrolyte I crossover hydrogen sweep exit stream (2007). Such a cell design is described in further detail in Example 1. In an embodiment, both electrodes may be dry, or not substantially flooded, allowing the electrodes to operate as electrolysis electrodes or fuel cell electrodes. In a preferred electrolysis-only embodiment, additional electrolyte (or anolyte) is fed to the oxygen electrode (anode) via an anolyte inlet stream (2008) using an anolyte circulation pump (2015) and exiting as an anolyte / oxygen mixture via the anolyte and oxygen exit stream (2009).

[0035] The electrolyte that is fed between the AEMs and electrodes is fed to an electrolyte and gas separation unit (2010) that separates electrolyte from any gas in the electrolyte layer, such as crossover hydrogen. The separation unit (2010) may be a vessel that uses gravity for separation of gas and liquid, it may be a membrane separator, it may use ultrasonic vibration, or it may use a sparging gas to assist separation of dissolved gas. The electrolyte from the separation unit (2010) may be recirculated back to the electrolysis cell stack (10) using the electrolyte circulation pump (2014). The crossover hydrogen may be vented via a crossover hydrogen exit stream (2016), or it may be captured and stored. It is possible for the sweep layer electrolyte (within 10) to be contaminated with oxygen from either oxygen crossover, or in the case of a stack of cells (10), from shunt currents in the electrolyte manifold. Shunt currents can cause electrolysis to occur in the electrolyte manifolds, thus evolving hydrogen and oxygen.

[0036] To remove oxygen from the hydrogen, a recombiner (described in Figure 3) could be advantageous if added to the exit stream (2016). In the preferred embodiment, the electrolytefrom the anode (i.e., anolyte) may be fed to an anolyte and oxygen separation unit (2011) to separate electrolyte from product oxygen. Product oxygen may be stored or vented via a product oxygen exit stream (2012). The anolyte from the anolyte and oxygen separation unit (2011) may be recycled back to the electrolysis cell stack (10) using an anolyte circulation pump (2015) via the anolyte inlet stream (2008). Dry hydrogen can exit the electrolysis cell stack (10) via the hydrogen product stream (2013).

[0037] By sweeping electrolyte between the electrodes, one skilled in the art can appreciate the significant advantages. The cell may operate at a low current and / or high pressure with thin AEMs for improved performance and efficiencies without dangerous hydrogen oxygen mixtures forming in the anode flow paths, and without the performance and efficiency sacrifices of using increasingly thick AEM membranes. The hydrogen that does cross into the electrolyte sweep layer (within 10) and exiting via the electrolyte I crossover hydrogen sweep exit stream 2007) may be recovered, thus improving hydrogen production efficiency. By including an AEM layer between the electrodes, pressure imbalances would not cause convective transfer of hydrogen into the oxygen or oxygen into the hydrogen. Further, the sweep layer may be monitored to detect inordinate quantities of hydrogen or oxygen. Such detection would allow a membrane or cell failure to be identified before dangerous mixtures form. Consequently, the disclosed design provides an inherently safe and efficient means to electrolyze water at high pressureExample 4 - System with Oxygen Recycle

[0038] An electrolysis system with oxygen recycled through a recombiner may also help prevent dangerous gas mixtures from forming during high pressure operation. Figure 5 shows a diagram of one embodiment of such a system design. In a preferred embodiment, liquid water isfed to an electrolysis cell stack (10) via a water inlet feed (3002). In the case of a PEM electrolysis cell stack, the water may be pure deionized water. In the case of an AEM electrolyzer, the water may be a component of aqueous electrolyte. During electrolysis operation, oxygen is produced in the anode, and an oxygen / liquid mixture exits that electrolysis cell stack (10) via the water and oxygen outlet. The product oxygen may contain crossover hydrogen. At higher hydrogen pressure or lower oxygen production rates, the percentage of hydrogen in the oxygen will be higher. Ultimately, the upper end of hydrogen pressure and the lower end of gas production is limited by the risk of forming unsafe gas mixtures. In a preferred embodiment, the oxygen and water or electrolyte are separated in a gas-liquid separation unit (3005). In a conventional design, the oxygen is typically vented. In the instant invention, a portion of the oxygen from the impure oxygen product stream (1007) may be passed through a recombiner (3007 and described in detail in Example 2) to remove hydrogen contamination. The cleaned oxygen exits from the recombiner via the pure oxygen and water product stream (3008), and at least a portion is then sent back to the electrolysis stack via the recycled clean oxygen feed stream (3004) using an oxygen recycle blower (3009) to reduce the concentration of hydrogen in the electrolyte and oxygen outlet (3003).

[0039] In one embodiment, as shown in Figure 5, the recycled oxygen may be fed directly into the cell stack oxygen. In an alternative embodiment, the recycled oxygen feed, alternate flow (element 3004a, dotted line) may be fed into the water and oxygen outlet stream (3003) just downstream of the cell stack. The ratio of recycled oxygen may be optimized for the electrolysis application to extend turn-down operation to lower values, or increase hydrogen operating pressure, while minimizing oxygen recycle blower parasitic. For example, if 50% of the oxygen outlet is recycled, the hydrogen concentration is cut in half, enabling approximately2X higher hydrogen pressure, or 2X lower turndown currents. Ultimately, product oxygen is vented from the system via the oxygen and water vent (3010), and product hydrogen is vented separately via the product hydrogen stream (3011).

[0040] What is claimed then, includes a high-pressure electrolyte system, having at least one electrolysis cell having at least a first electrode and a second electrode, and in which at least one of the electrodes produces hydrogen at a pressure of greater than 30 bar. The at least first and the at least second electrode may be separated by at least one non-electrode electrolyte sweep layer. A liquid electrolyte may recirculate from the electrolyte sweep area to an electrolyte and gas separation unit, and hydrogen may evolve from the recirculating electrolyte sweep area within the electrolyte and gas separation unit.

[0041] The system may have at least one anion exchange membranes (AEM) that separates hydrogen and oxygen separation during gas evolution, and at least one anion exchange membrane (AEM) may separate at least one product gas and the liquid electrolyte sweep layer. Hydrogen evolved within the electrolyte and gas separation unit may be purified with a recombiner.

[0042] In another embodiment, a high pressure electrolysis system producing hydrogen at pressures of at least equal to or greater than 30 bar may be constructed, where at least a portion of an evolved oxygen product is recirculated through a recombiner to remove hydrogen contamination and recirculation of the portion of the purified product oxygen gas is blended with product oxygen In other embodiments, hydrogen may be produced at pressures of at least equal to or greater than 100 bar, 250 bar, 350 bar, 500 bar, 900 bar, or possibly greater.

[0043] In yet another embodiment, an electrolysis system producing hydrogen at a pressure of at least equal to or greater than 2 bar may be constructed, including at least, an anionexchange membrane (AEM) separating evolved hydrogen and oxygen, wherein the AEM is equal to or less than 100 microns thick, and where a portion of oxygen product gas is recirculated through a recombiner to remove hydrogen contamination, and at least a portion of oxygen product gas is blended with the oxygen product gas. Such a system may be configured to produce hydrogen at a pressure of at least equal to or greater than 10 bar, 30 bar, or possibly more. In various embodiments the anion exchange membrane (AEM) is equal to or less than 75 microns thick, equal to or less than 50 microns thick, membrane may be equal to or less than 25 microns thick.

[0044] Numerous alterations, modifications, and variations of the preferred embodiments disclosed herein will be apparent to those skilled in the art and they are all anticipated and contemplated to be within the spirit and scope of the disclosed specification. For example, although specific embodiments have been described in detail, those with skill in the art will understand that the preceding embodiments and variations can be modified to incorporate various types of substitute and or additional or alternative materials, relative arrangement of elements, order of steps and additional steps, and dimensional configurations.

[0045] Accordingly, even though only few variations of the products and methods are described herein, it is to be understood that the practice of such additional modifications and variations and the equivalents thereof, are within the spirit and scope of the method and products as defined in the following claims. The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or acts for performing the functions in combination with other claimed elements as specifically claimed.

Claims

WE CLAIM:

1. A high pressure electrolyte system, comprising: a. at least one electrolysis cell having at least a first electrode and a second electrode, b. wherein at least one of the electrodes produces hydrogen at a pressure greater than30 bar, c. wherein the at least first and the at least second electrode are separated by at least one non-electrode electrolyte sweep layer, d. wherein a liquid electrolyte recirculates from the electrolyte sweep area to an electrolyte and gas separation unit, and e. wherein hydrogen is evolved from the recirculating electrolyte sweep area within the electrolyte and gas separation unit.

2. The system according to claim 1, wherein at least one anion exchange membranes (AEM) layer in the cell stack separates hydrogen and oxygen during gas evolution.

3. The system according to claim 1, wherein at least one anion exchange membrane (AEM) separates at least one product gas and the liquid electrolyte sweep layer.

4. The system according to claim 1, wherein hydrogen evolved within the electrolyte and gas separation layer is purified with a recombiner.

5. A high pressure electrolysis system producing hydrogen at pressures of at least equal to or greater than 30 bar, wherein at least a portion of an evolved oxygen product is recirculated through a recombiner to remove hydrogen contamination and recirculation of the portion of the purified product oxygen gas is blended with product oxygen.

6. The device according to claim 5, wherein hydrogen is produced at pressures of at least equal to or greater than 100 bar.

7. The device according to claim 5, wherein hydrogen is produced at pressures of at least equal to or greater than 250 bar.

8. The device according to claim 5, wherein hydrogen is produced at pressures of at least equal to or greater than 350 bar.

9. The device according to claim 5, wherein hydrogen is produced at pressures of at least equal to or greater than 500 bar.

10. The device according to claim 5, wherein hydrogen is produced at pressures of at least equal to or greater than 900 bar.11 . An electrolysis system producing hydrogen at a pressure of at least equal to or greater than 2 bar, comprising: a. an anion exchange membrane (AEM) separating evolved hydrogen and oxygen, wherein the AEM is equal to or less than 100 microns thick, b. a portion of impure oxygen product gas is recirculated through a recombiner to remove hydrogen contamination, and c. at least a portion of purified oxygen product gas is recycled and blended with the impure oxygen product gas.

12. The system according to claim 11, wherein the system produces hydrogen at a pressure of at least equal to or greater than 10 bar.

13. The system according to claim 11, wherein the system produces hydrogen at a pressure of at least equal to or greater than 30 bar.

14. The system according to claim 11, wherein the anion exchange membrane (AEM) is equal to or less than 75 microns thick.

15. The system according to claim 11, wherein the anion exchange membrane (AEM) is equal to or less than 50 microns thick.

16. The system according to claim 11, wherein the anion exchange membrane (AEM) is equal to or less than 25 microns thick.

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