ELECTROCHEMICAL CELL PLANT

Abstract

A system comprising a stack of electrolyzers connected to a water / gas separation vessel, via inlet and outlet pipes, wherein the separation vessel is adapted to passively separate water and gas; the separation vessel contains a heat exchanger; and the separation vessel is constructed from a polymeric material.

Description

ELECTROCHEMICAL CELL PLANT FIELD OF INVENTION The present invention relates to electrolyzer systems and the separation and cooling of water and gas. BACKGROUND OF THE INVENTION Conventionally, water electrolysis systems vent oxygen and reject heat to the atmosphere, with hydrogen being the valuable component. This green hydrogen, produced from renewable sources through electrolysis, is used in a constantly expanding range of applications. Examples of such applications include transportation fuel, long-term energy storage, and renewable chemistry. Traditionally, electrolyzer stacks are connected to a heat exchanger and associated pumps via multiple pipes. The pumps / heat exchangers are then connected to a gas separation tower. The water and oxygen produced by the electrolyzer stacks are fed through pipes to separate pumps / heat exchangers for cooling, and then the oxygen and hydrogen are fed to the separate gas separation tower. The cooled water is then returned through pipes to the electrolyzer stacks. Traditionally, these components are positioned separately and connected by long distances of piping. This is due to the industry's preference for using a single large pump (which is perceived as cheaper / easier).In this system, water needs to be pumped back and forth over long distances, which can lead to pressure losses and the material cost of requiring more piping. There is also a significant number of plants involved in these systems. The separate location of the components and the long distances between them also mean that it is not possible to perform tests at a single site where all the pumps, the heat exchanger, and the electrolyzer stacks are located. This is not ideal because the final system cannot be tested before it is built. qa / οηη / ζζηζ / Ε / γίΛΐ 2 / 11 Electrolyzer systems of the prior art therefore comprise elements that cannot be manufactured in an efficient factory environment. Instead, they require multiple links to be assembled in the field, without prior testing. Oxygen and heat are also becoming valuable byproducts of electrolysis (rather than hydrogen being the only valuable product). To extract these byproducts, parts are added to electrolyzer systems instead of being efficiently integrated. These parts are typically metal-based. Conventional manufacturing techniques generally relied upon include metal fusion welding, flange joint assemblies with wrenches, and field piping assembly with little regard for the number of parts deployed; this leads to considerable manufacturing difficulties in a modern plant deployment scheme. Currently, in the design of electrolysis plants, the process engineering discipline establishes generic and segregated process equipment comprising electrolyzer stacks, piping, a heat exchanger (which extracts heat from the processed water), more piping, a 'elimination' separation tower (which separates water and gaseous oxygen), multi-flange joints (with nuts, bolts, and tie rods), pump skids, a glycol tank with piping, and associated airflow cooling (along with primary cooling). Extensive fabrication is also required to pack these together and connect them to large-bore drill pipes with trace heating, thermal compensation, and structural supports (weight hangers, struts, etc.). These are further complemented by novel oxygen recovery schemes, hydrogen and / or oxygen compression, gas storage, and heat recovery.These components are sometimes positioned along long distances and contribute to a large space occupied, which in turn justifies larger diameter pipes, assembly complexity, and high cost. The present invention provides a system that includes a compact oxygen separation vessel that is durable and cost-effective to manufacture. BRIEF SUMMARY OF THE INVENTION The present invention is a complete, efficient, and environmentally sustainable water electrolysis system (water cooling and water gas separation), which qa / οηη / ζζηζ / Ε / γίΛΐ 3 / 11 can be fully built, in repeatable units, in a factory environment. It can also be factory-tested before on-site deployment, which offers numerous benefits, such as maintaining a high standard of cleanliness. The entire system is located in a single site, with short distances for water and gases to travel. This provides both economic and environmental advantages. Therefore, according to a first aspect of the invention, a system comprises a stack of electrolyzers connected to a water / gas separation vessel, via inlet and outlet pipes, wherein: The separation vessel is adapted to passively separate water and gas; The separation vessel contains a heat exchanger; and the separation vessel is constructed of a polymeric material. According to a second aspect of the invention, a process for electrolyzing water uses the system as defined above, wherein the gas / water separation vessel contains water, and wherein the electrolyzer electrolyzes the water to produce hydrogen and oxygen, which then flow through a pipe to the separation vessel, where both the hydrogen and oxygen are passively separated from the water and extracted from the system. According to a third aspect of the invention, an oxygen separation vessel is provided for passively separating water from an oxygen and water mixture. The vessel comprises: a plurality of inlet nozzles for receiving the oxygen and water mixture; a heat exchanger positioned within the vessel for cooling the oxygen and water mixture; at least one oxygen outlet for discharging oxygen separated from the oxygen and water mixture; and at least one water outlet nozzle for discharging water separated from the oxygen and water mixture. The vessel described in the third aspect can be used in combination with the system and methods described in the first and second aspects, respectively. The vessel described in the third aspect is preferably intended for use in combination with an electrolyzer stack, for example, an electrolyzer stack for producing hydrogen. The third aspect vessel provides an oxygen separation vessel that is rugged, compact, and cost-effective to manufacture. qa / οηη / ζζηζ / Ε / γίΛΐ 4 / 11 Having multiple inlet nozzles leads to the creation of multiple columns of the mixture within the vessel in use, which greatly improves the oxygen / water separation rate for a given vessel height, allowing the vessel to be much shorter than conventional oxygen separation vessels. For example, a vessel according to the present invention can be approximately 2.5 m high, whereas conventional vessels are typically about three times this height. There can be two inlet nozzles, three inlet nozzles, four inlet nozzles, five inlet nozzles, or any other number of inlet nozzles greater than one. Preferably, there are three inlet nozzles, which allows for the creation of three columns of the mixture. In addition, having an oxygen separation system that includes a heat exchanger (i.e., the heat exchange is inside the oxygen separation vessel) is unconventional and reduces the power required to pump the water out of the vessel. In conventional systems, the heat exchanger is positioned downstream of the oxygen separation vessel, with a pump positioned between the oxygen separation vessel and the heat exchanger. In this conventional arrangement, the pump is positioned upstream of the heat exchanger to overcome the pressure drop across the heat exchanger. Positioning the heat exchanger inside the vessel means that the electrochemically generated oxygen pressure (i.e., generated during electrolysis) leads to an increase in pressure within the vessel, which in turn applies pressure to the free liquid surface of the water inside the vessel. This pressure helps overcome the pressure drop across the heat exchanger, which consequently means that the pump power can be reduced. This arrangement allows for an 18% reduction in pump power, leading to considerable electricity savings. Since the energy used by the pump during electrolysis is considered 'parasitic' energy, this reduction effectively lowers the cost of hydrogen production. This is especially important in low-power scenarios, such as when the electrolyzer is powered by solar panels on a cloudy day or by wind turbines on a calm day. In these low-power scenarios, qa / on / z / z / Ε / γίΛΐ 5 / 11 power, the power required by the pump can represent a significant proportion of the total power consumed. Preferably, the container (i.e., the main body of the container) is constructed from a plastic / polymer material. The container may be constructed from partially cross-linked linear low-density polyethylene (LLDPE) (such as ICORENE® LLDPE). Alternatively, the container may be constructed from high-performance hexane-density polyethylene. Preferably, the inlet nozzles are positioned at or near the top of the oxygen separation vessel. Near the top means that the nozzles are positioned in a defined region above 25% of the vessel in use, more preferably within the top 10% of the vessel. Positioning the inlet nozzles near the top of the vessel means that the multiple columns of the mixture created by the inlet vessels are larger / taller, allowing for better water / oxygen separation. The container may further comprise at least one through hole for receiving a transverse reinforcing element, preferably wherein at least one through hole has a substantially rectangular or substantially elliptical cross section. Through holes may also be called through openings, through channels, or similar terms. Through-holes allow the vessel to be fitted with transverse elements that reinforce / strengthen it. During use, high pressures are experienced inside the vessel, which could otherwise cause buckling or rupture. Furthermore, the through-holes themselves also improve the vessel's strength by bridging the side walls and provide vacuum stability against the vacuum that can occur as a result of the pump's negative suction pressure (i.e., the through-holes provide a reinforcing effect even in the absence of additional reinforcement). qa / οηη / ζζηζ / Ε / γίΛΐ 6 / 11 The use of through holes with a rectangular or square cross-section is particularly preferred because it facilitates homogeneity of the wall thickness of the polymer / plastic coating during manufacturing, thus simplifying the manufacturing process. Preferably, the vessel further comprises a transverse reinforcing element received in at least one through-hole. Each through-hole may have a transverse reinforcing element. The transverse reinforcing element is preferably made of steel. The transverse reinforcing element may be a tie rod or similar. The reinforcing elements may alternatively be referred to as reinforcement members or similar. Preferably, the container further comprises an external sheet lining that covers at least part of the container's external surface. Preferably, the lining is made of steel, such as a pressure-formed steel plate (e.g., pressure-formed steel plate EN10028 P460). The lining may also be provided as a fiberglass reinforcement. Also known as glass-reinforced plastic (GRP), the fiberglass reinforcement may be used with linings of linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), polypropylene (PP), or high-density polyethylene (HDPE). The lining reinforces the vessel and increases the pressures it can withstand. While the lining and cross-bracing elements alone provide a substantial reinforcing effect, the use of lining and cross-bracing elements in combination further enhances the reinforcing effect because it helps to distribute the load exerted by the bracing elements across the vessel's side walls, thereby increasing the load the vessel can withstand before breaking or buckling. The vessel may alternatively have at least one circumferential groove to receive a circumferential reinforcing element. For example, such a circumferential reinforcing element may be a steel ring or similar component that reinforces the vessel. Preferably, the container further comprises two external end plates arranged at opposite ends of the container, wherein the external end plates are coupled by one or more longitudinal reinforcing elements. Such end plates and longitudinal reinforcement elements provide additional strength to the vessel. Preferably, the end plate is made of steel, qa / on / ζζηζ / Ε / γίΛΐ 7 / 11 as EN10028 P460 pressure steel plate or P350 steel or 300 series stainless steel of suitable thickness. The reinforcing elements are also preferably made of steel. The reinforcing elements may be tie rods or similar. Optionally, the plurality of inlet nozzles and at least one water outlet nozzle can be integral with the vessel and constructed of the same material as the vessel, preferably where the nozzles are connected to the pipes by polymer fusion, which is very cost-effective. Preferably, the inlet nozzles are arranged so that they are positioned substantially at the same height (i.e., when the gas separation is in the orientation in which it is used). "Substantially" means that they are at the same height within a 10% deviation of the total height of the vessel. Preferably, the container is rotationally molded in a single, one-step process. Preferably, the container has a flat oval cross-section, with flat side walls that are positioned vertically in use. Even more preferably, the inlet nozzles are positioned so that, in use, they direct the fluid flow towards a (preferably flat) side wall of the vessel, creating a cyclonic effect. This increases the efficiency of the water / oxygen separation process, allowing the vessel to be even more compact. In other words, the inlet nozzles can be positioned so that, in use, they direct the fluid flow along the curvature of one side wall of the vessel and towards an opposite side wall, so that centrifugal force is used to enhance fluid mixing and gas separation. Preferably, the container is constructed of high-performance hexane-density polyethylene. It is clean, rigid, and offers high resistance to environmental stress cracking. Alternatively, the container can be constructed of other materials, such as partially cross-linked linear low-density polyethylene. Optionally, the vessel may have a conical collector located between the heat exchanger and at least one water outlet nozzle. This increases the fluid flow velocity through the water outlet nozzle. qa / οηη / ζζηζ / Ε / γίΛΐ 8 / 11 Optionally, the heat exchanger can be a tube heat exchanger. Preferably, the oxygen separation vessel further comprises a sleeve arranged around the tubular heat exchanger, preferably wherein the sleeve is made of polymeric material. Preferably, the sleeve comprises an inlet, an outlet, and one or more baffle plates arranged to cause the fluid to flow in a crossflow direction around the heat exchanger when in use. The baffles maximize fluid disruption at the boundary layer between the fluid and the heat exchanger, thereby improving heat exchange. Crossflow means that the fluid flows in a direction with a non-zero component perpendicular to the tubular extension of the heat exchanger. According to a fourth aspect of the invention, a system for generating hydrogen is provided, which comprises a stack of electrolyzers connected to the oxygen separation vessel of the third aspect. Preferably, the system further comprises a pump connected to at least one water outlet nozzle, wherein the pump is located downstream of the oxygen separation vessel. As discussed previously, having the pump downstream of the gas separation vessel allows for a reduction in pump power, thereby saving electricity. The pump drives a flow of water out of the oxygen separation vessel. DESCRIPTION OF THE FIGURES Figure 1 shows a schematic of a preferred embodiment of the present invention. Figure 2 is a graph showing that, in a 2 MW system, pump savings can reach up to 1.5% of total energy use. When the plant is idle, with the pumps running, savings of up to 70% of the plant's current energy consumption could be achieved. Figure 3 is a schematic showing the fluid flow in a preferred embodiment of the invention (only the container is shown). qa / οηη / ζζηζ / Ε / γίΛΐ 9 / 11 Figure 4 is a schematic showing a preferred embodiment of the present invention. Figures 5a-c show a first configuration of a container. Figures 6a-d show a second configuration of a container. Figures 7a-d show a third configuration of a container. Figures 8a-d show a fourth configuration of a vessel. LABELS ON THE FIGURES 1. Heat Exchange Separation Phases O2 one-time pressure molded vessel (1a, 1b and 1c represent various vessel configurations). 2. Secondary Cooling Circuit. 3. Pump. 4. Electrolysis cell(s). 5. Heat exchanger(s). 6. Molded nozzles (6a are inlet nozzles / ports, 6b are outlet nozzles / ports). 7. Cold feeding. 8. Hot Exit. 9. Water / oxygen mixture. 10. Pressure reliever. 11. Primary cooling circuit. 12. Wall of up to 3 layers. 13. Composite material pressure casing. 14. Antimicrobial additive. 15. Region of turbulence created. 16. H2O collector. 17. Cup slots. 18. Refrigerant inlet port. 19. Refrigerant outlet port. 20. Internal duct. 21. Through the hole. 22. Oxygen outlet. qa / onn / zznz / E / YiAi 10 / 11 23. Exterior cladding. 24. Transverse tie rod. 25. End plate. 26. Longitudinal tie rod. DESCRIPTION OF PREFERRED REALIZATIONS As used in this specification, electrolyzer stacks and water / gas separation vessels (or towers) are terms used in the art. A stack comprises a plurality of electrolyzer cells. As used in this document, heat exchanger is a well-known term in the art. In the context of electrolyzers, these cool the water flowing through an electrolyzer system. The inventors have devised an electrolyzer system comprising a multipurpose container, which combines large storage of clean water, separation of oxygen and / or hydrogen from water, heat exchange and, optionally, manufacturing without openings (i.e., avoiding the need to manufacture and add additional ports) and increased cleanliness in a single module. The advantage of the invention is that it allows for multiple self-contained electrolysis modules, i.e., repeatable and manageable units, unlike the previous technique which requires electrolyzers to be assembled on-site with pipes, separation towers and pumps, and then tested. The oxygen separation vessel of the present invention is also smaller than conventional separation vessels, which facilitates its transport and installation and allows its installation in smaller spaces. The core of the invention includes a twofold modification to existing systems. First, locating a heat exchanger within a gas separation tower reduces the plant's balance and increases efficiency. Second, the consolidated heat exchanger and gas separation unit can be coupled to the electrolyzer at a short distance (since the components are compatible), further increasing system efficiency. Previously, due to the plant's high balance, the electrolyzer stacks had to be connected via a [qa / οηη / ζζηζ / E / γίΛΐ] The 11 / 11 distance was much greater, requiring a large water / gas separation tower and a separate heat exchanger. This made on-site assembly and testing very difficult. The gas separation vessel is constructed from a polymeric material. Preferably, it is made from a plastic material. The gas separation vessel can be constructed from partially cross-linked linear low-density polyethylene (LLDPE) (such as ICORENE® LLDPE) or high-performance hexane-containing high-density polyethylene. Furthermore, the gas separation vessel can have a multi-walled construction, with a pressure-formed steel plate as the outer lining or liner (such as EN 10028 P460 or P350 steel or 300 series stainless steel of suitable thickness). Alternatively, the outer lining or liner can be reinforced with fiberglass. The separation vessel preferably comprises a plurality of nozzles for connecting the inlet and outlet pipes, wherein the pipes are integral with the vessel and are constructed of the same polymeric material as the vessel. This offers many manufacturing advantages. In a preferred embodiment, the container comprises at least 4 nozzles, with at least 2 nozzles adapted to be in fluid communication with each pipe. More preferably, the system comprises at least 6 nozzles, wherein at least 3 nozzles are adapted to be in fluid communication with each pipe. Preferably, the vessel (which preferably includes the nozzles) is injection molded or rotationally molded in a single, one-step process from a polymeric material. More preferably, the piping is also constructed from a polymeric material. This is advantageous because the various components can then be connected by polymer fusion. This eliminates the need for metalworking and complicated flanges as in the prior art. The reduced number of parts in a system of the invention leads to design efficiency and ease of implementation; this can be achieved in the proposed invention by means of a rotational molding technique, which generates up to 15 ports / nozzles directly into the vessel walls. These nozzles can then be connected directly to the piping by means of automated fusion welding. 12 / 11 polymers, which does not require conventional fusion welder qualification, tabs, keys, gaskets, nuts, bolts and washers and also guarantees leak-proof sealing. The segregated location of auxiliary components (tower and associated equipment) in the prior art, far from the hydrogen generation unit (fuel pile), necessitates the calculation of numerous parts (due to the large diameters, forces, and weight involved) and creates difficulties in flow management and cleanup. For example, heavy objects must be lifted on-site for assembly, with pipe ends potentially exposed to components at the construction site. A system of the invention is shown in Figure 1. In a system of the invention, water from the electrolyzer stack(s) is fed to the consolidated gas separation and heat exchanger unit. In this consolidated unit, the heat exchanger is submerged in the water flowing into the gas separation tower, which is in use, and serves to cool the surrounding water. This cooled water is then fed back to the electrolyzer. In a preferred embodiment, the electrolyzer stack is connected to the separation vessel over a short distance, so that they can be located in the same building, and preferably very close to each other. Reducing the distance between the electrolyzer stack and the integrated heat exchanger and gas separation unit avoids the various drawbacks of the prior art, such as the economic implications of transporting and pumping water over long distances. The present invention consolidates the auxiliary functions of electrolysis into a lowest common denominator (module) using design and assembly rules relevant to lightweight assembly (low parts count, streamlined interfaces), and establishes all manufacturing and testing under one roof in a controlled environment. Forming the product in such an architecture benefits the organization in several ways: first, it standardizes the auxiliary functions with a focus on compatibility; second, it reduces parts inventory and improves quality (e.g., the number of pump parts); third, it reduces inventory (and all administrative tasks), manufacturing cycle time, and also minimizes on-site installation time. The present invention can employ 'snap and go' piping, as it is constructed from polymeric materials. The system is then qa / oni / zzi / e / γίΛΐ 13 / 11 can be connected via integral nozzles, and small-diameter pipes of less than 50 mm can be used, reducing worker strain and the need for heavy equipment; this task is now better described as a trivial plumbing job. This contrasts sharply with the use of a 350 mm inner diameter in the prior art, which is better described as a heavy-industrial task. The present invention reduces the space occupied, pump losses, and the possibility of dirt ingress, as it can be assembled in a factory environment. The present invention is preferably manufactured by a single-action injection molding method. This offers advantages in terms of ease of manufacture. It is also preferably formed by rotational molding. This allows for rapid manufacturing. In a preferred embodiment, the container is insulated to allow for preheating, convenient adjustment of instruments (conductivity, water level, and temperature measurements), and prevention of microbial growth. In a preferred embodiment, the polymeric container of the invention comprises an antibacterial or antifungal agent. Such agents are known in the art. The agent can be provided by incorporating an additive during the molding process, preferably in a residue-free, recyclable thermoplastic mold. The vessel of the invention allows for complete factory assembly, integration, and testing, with close integration to the stacks. This results in a smaller internal diameter, shorter piping lengths with less pressure loss, and eliminates the need for flanges and ports, leading to assembly time savings, reduced leak likelihood, lower charging pressure, and less need for flow management. This is because the system components are no longer located far from the electrolyzer stack or from each other. The invention reduces the number of parts, complexity, and energy consumption in pumping. Several factors contribute to the significant energy savings of the pump. A typical embodiment of the invention will reduce losses through the heat exchanger arrangement (see Figure 2), the shorter length of the pipes (the beneficial aspect being reduced friction losses), and the ability to use a multistage pump, which allows for energy-saving adjustments to a greater degree than would be possible without the invention. qa / οηη / ζζηζ / Ε / γίΛΐ 14 / 11 In a preferred embodiment, the vessel has a flat oval cross-section with vertically positioned, flat side walls. This embodiment is shown in Figure 3. Preferably, the nozzles are positioned so that, in use, they direct the fluid flow toward a (preferably flat) side wall of the vessel, creating a cyclonic or centrifugal effect. The nozzles direct the fluid flow along the curvature of one side wall of the vessel and toward an opposite side wall. This is also shown in Figure 3. Preferably, the fluid flow is directed at an angle of approximately 45 degrees to the side wall, creating a turbulent region, or cyclone. This enables efficient water / gas separation.The nozzle angle (i.e., the inlet nozzle) can be between 30 and 60 degrees, more preferably between 35 and 55 degrees, even more preferably between 40 and 50 degrees, and most preferably around 45 degrees (i.e., between 44 and 46 degrees). A wire brush may be located inside at least one of the nozzles, so that the kinetic energy of the fluid stream is interrupted during use. In a preferred embodiment, a vortex switch, a vortex deflector or an anti-fog pad is located inside at least one of the pipes. In a preferred embodiment, the vessel's proportions are such that the height-to-width ratio is less than 3:1 or 2:1, or preferably around 1:1. Without intending to impose any theory, this may be possible because the nozzles direct the fluid flow to a side wall, creating a cyclonic / centrifugal effect. This allows for more effective water / gas separation and means the separation vessel does not need to be as tall as those of the prior art. The vessels of the prior art are mostly vertical with a height-to-width ratio of 6:1 for proper gas and water separation. This prevents the water-gas mixture from being readmitted into the pump inlet. Fusion-welded, polymer-based vessels with a 6:1 ratio are ergonomically difficult to handle from a manufacturing standpoint. They are fragile and prone to breakage, thus requiring additional costly precautions. In a preferred embodiment of the invention, with its split ports (multiple nozzles) and a 1:1 ratio, the ease of manufacturing of the vessel itself is improved. 15 / 11 container is achieved by a rotational molding process and cleaning on the process side is achieved without burrs, by joining the flanges or by manually drilling or deburring the plastics (these features are an integral part of molding in a one-step process). The gas separation 'elimination' towers used in prior art systems comprise a column 1 m in diameter by 6 m high (totaling 4.8 m³), ​​which is impractical to handle and manufacture in a fully equipped factory and difficult to export (via land or sea transport) or assemble on-site. This limits the scope for the effective deployment of a series of units. In contrast, the typical aspect ratio of a typical embodiment of the proposed invention is a parallelepiped of 2.6 m x 2.6 m x 1 m (totaling 6.8 m³); a much more practical load to handle effectively. In the state of the art, many tabs are joined one by one, screwed on-site to the tower (since the finished assembly is too large to transport in one piece), which involves inefficient practices and tools and these are, at least initially, prone to more leaks that need to be repaired on-site. The heat exchanger for use in the invention is preferably a tube heat exchanger. This heat exchanger operates with a coolant supply, preferably cold water, flowing through the interior of its tube-like structure. This cooled metal exterior then cools the surrounding water within the gas separation tower, which is fed from the electrolyzer stack. The process fluid is drawn through the shell side and into the pump inlet, while the tube side of the heat exchanger is connected to a coolant circuit. In the prior art, the heat exchanger is located downstream of the pump. In the present invention, the heat exchanger is located upstream of the process pump.In the case of the present invention, the pressure drop across the heat exchanger is overcome by the electrochemically generated oxygen pressure and specifically by the absolute pressure applied to the free surface of the liquid in the suction vessel. Therefore, the pump power can be reduced accordingly. A reduction in pressure drop of 0.6 per 1 bar g would give / onηη / ζζηζ / E / γίΛΐ. 16 / 11 results in a reduction of pump power of approximately 10 to 16%. (The total pressure drop is approximately 6 bar in this system). The present invention considerably reduces the footprint and number of parts, and, with a variety of seamless nozzles, increases manufacturing capacity. The present invention allows for a diversity of refrigerant types through the specific selection of the heat exchanger type (enabling multiple downstream integration possibilities), the virtual elimination of pump pressure drop from the primary cooling side by preventing parasitic pump losses at reduced operating speeds, and also provides pressure oxygen capacity and integrated antimicrobial measures that ensure maximum cleanliness during downtime. In a preferred embodiment, the heat exchanger, preferably a tube heat exchanger, is located in the highest flow region of the vessel, thus avoiding considerable flow resistance on the shell side of the vessel compared to a conventional plate heat exchanger. This reduces pump losses compared to a conventional plate heat exchanger (made of multiple narrow, fluid-filled impact openings). The pressure head savings were evaluated using pump affinity laws, which govern water circulation based on centrifugal pumps, and yielded a minimum pump energy saving of 14%. This figure is achievable only by reducing the pressure head across the floating tube heat exchanger.In addition to this, the tube heat exchanger is made from a single manufactured piece compared to the plate heat exchanger which normally comprises a plurality of plates, seals, end plates, studs, washers, and nuts. The robustness and versatility of the selected heat exchanger type can be affirmed in terms of chemical longevity, chemical resistance to salt, tolerance to debris and fouling, and low pressure drop. The cooler stream is on the tube side (it flows internally, on the tube side). This is unusual and actually decreases the heat exchange coefficient (the ability to dissipate heat); conventionally, this would not be adopted. However, the reduction in the heat exchange coefficient is very modest and does not constitute a significant compromise. The other advantages more than compensate for this, because the larger pump and flow are qa / oni / zzi / e / γίΛΐ 17 / 11 on the electrolysis side, and this more than compensates for this negative aspect. This arrangement allows the use of a variety of refrigerant types on the tube side (internally), which the shell side cannot accommodate, and consequently, a significant reduction in the amount of equipment on the secondary cooling side. The system of the invention opens the possibility of using natural waterways or seawater as a coolant in the electrolysis process. In large swimming complexes, district heating systems, or industrial spaces, the heat exchanger could be tolerant of chlorinated water or inhibitors, and the heat can be recovered, increasing the overall efficiency toward a fully passive system standard. Tests have shown that energy efficiency >95% can be achieved in some cases. A key benefit of the present invention is the permissible type of coolant and the specification that it can be any approximately filtered fluid supplied at a temperature ranging from above freezing to 40°C. A coolant such as seawater or water from waterways is not normally considered, but this is made possible by the invention.This overcomes the narrow concern of heat exchange performance, prioritizing system integration and space utilization. Cooling primary process water is particularly attractive in offshore applications, such as offshore wind turbines, enabling a significant reduction in footprint and paving the way for future wind turbine integration. The size of the stack modules to be associated with the module can also be carefully selected to match the 690 V DC link voltage of the wind turbine's Type IV (suitable for electrolysis). Therefore, a system of the invention can be adapted to have 300 to 350 electrochemical cells as standard. It is important to match the DC voltage of the electron donor (wind turbine) with the load voltage (electrolyzer).The present invention can define a container volume that adapts to the batteries it will receive. In the present invention, the required length of ducts or pipes is reduced due to the placement and fusion of auxiliary elements. This results in a significant number of parts and space saved (the pipe length is the obvious one, but elbows, unions, flanges, isolation valves, filters, metal bellows, pipe hangers, anchors, sheathing, heat tracing, all add more). 18 / 11 pressure drop, etc.) and will lead to a minimal reduction in pump power of 1% (this is a conservative estimate as it only considers the reduction in pipe length). A pressure drop reduction of 0.6 to 1 bar from 6 bar (common in PEM electrolyzer stacks), due to the repositioning of the heat exchanger that utilizes the pressure generated on the liquid surface in the tank, will reduce pump power by 10–16%. An ideal situation is to achieve the largest possible inside diameter over the shortest possible length. This points the way to genuine optimized development with respect to head lift and parasitic pressure drop. This approach is not natural for many engineers, whose natural tendency is to add parts, not reduce them. In a preferred embodiment, the invention uses a centrifugal pump, preferably a multistage centrifugal pump. The preferred location of the pump is shown in Figure 1, namely, in the pipe leading from the separation vessel to the electrolyzer stack. A multistage centrifugal pump is preferred for the invention because of its superior throttling potential compared to single-impeller pumps and because it offers the best energy-saving synergy. 'Throtting' is typically invoked when hydrogen demand is low and the primary coolant flow requirement is reduced. With partial or reduced hydrogen demand, less fluid needs to be pumped around the system; this is referred to as 'throttling'.The general idea is to reduce the pump speed to lower energy consumption, which is highly beneficial since pump applications consume 20% of global energy, and environmentally friendly systems should be a model of energy conservation. This is even more relevant for widely deployed electrolysis systems that use very large pumps, as in the system of the invention. It also generates significant savings in operating costs for the customer and offers a competitive advantage. In a preferred embodiment, the pump is one that can achieve a lower shaft speed for the same output flow rate. This is called reduction capacity; in other words, a pump of the invention preferably has a good reduction capacity. It is expected that this reduction will save up to 40% of the pump's energy consumption if properly designed. A multistage centrifugal pump allows for greater reduction when speed is used to control the pump and, as the laws of affinity state, a greater qa / onοηη / ζζηζ / E / γίΛΐ 19 / 11 Speed ​​reduction results in a further reduction of kilowatt-hours used. The synergy of pump selection with the present invention reduces the head pressure and, consequently, the number of pump stages can be optimized (from 6 to 3 stages; see Figure 2), in addition to benefiting from the reduction capacity (37% is typical for multi-stage pumps compared to 5% for a single impeller); it is claimed that this reduces the power used beyond what can normally be achieved with a multi-stage or single-impeller pump and thus constitutes the advantage of this feature. In the field of gas-liquid two-phase separation, the separation technology is varied. Vertical demountable towers, as mentioned earlier, are the simplest and most common state-of-the-art form, but they suffer from the slowest separation rate and the largest footprint. This is because they rely on the residence time of the gas-water mixture (and a minimum column height is required to accommodate this) and gravity to allow the water to sink and the gas bubbles to rise to the top of the vessel at a collection point. Figure 1 shows three nozzles connected to each pipe. This preferred embodiment thus divides the flow and height by a maximum of three, leading to the typical choice of 2.6 m height mentioned earlier. This results in more efficient separation. In one embodiment, the present invention includes a Schoepentoeter device, which divides the mixed-phase feed stream into a series of lateral and curved flow streams. These curved streams dissipate the kinetic energy of the flows for smooth entry into the vessel and also provide centrifugal acceleration to promote liquid-gas separation. In some embodiments, a tangential cyclone is created in the separation vessel. This relies on centrifugal acceleration to separate the gas and water. Figure 3 shows how this can be achieved, i.e., by directing the fluid flow toward the side walls of the separation vessel at an angle. In a preferred embodiment, the nozzles are provided tangentially or nearly tangentially to create centrifugal acceleration (this mechanism increases the separation efficiency). This is shown in Figure 3. The nozzles direct the flow against the vessel walls and, once it hits the bottom, it envelops or swirls around. 20 / 11 of the heat exchanger following the lower curvature of the vessel, mimicking the effect of the baffles arranged around a conventional refrigeration heat exchanger. The eddies and turbulence around the tube heat exchanger are beneficial. There is potentially a large number of nozzles in the vessel of the invention. However, this does not add any complication since the nozzles are molded as part of the unique rotational molding vessel. In a preferred embodiment, the present invention involves the use of anti-fog pads consisting of fine mesh or grids to further eliminate vapor mist once separation has been achieved. Additional features also include a vortex switch and a vortex spoiler. In one embodiment, the kinetic energy of the streams is interrupted by a set of wire brushes located coaxially with the inlet nozzles. These types of brushes are known to be cost-effective in small air-gas separators. In a preferred embodiment, the vessel walls may include foam insulation (to reduce radiated heat during shutdown) and a three-walled construction consisting of polypropylene, foam, and polypropylene. Lighter weight, easier handling, cleaning, bacterial resistance, and the ability to be deployed in large, small, and specific environments alike (such as containerized packaging facilitated by the relevant aspect ratio or within a single-story building) are defining utility features; capable of serving all market segments since multiple modules are efficiently interconnected by small-diameter piping. The reduction in the number of parts is significant. The unique vessel is designed for the most demanding applications.The module can be manufactured in a factory at a much faster rate than current technology (currently reducing the time to manufacture equivalent vessels from 4 days to a few hours, and eliminating the lengthy deburring stage from 2 weeks to zero). Current alkaline units inherit heavy industrial construction methods, intensive component design, corrosion-prone systems, and outdated chemistry from the prior art. For example, many competing companies successfully attempt designs such as chlorine-alkali conversions to water electrolysis, but these are outdated because, when formulated, little attention was paid to quality control. 21 / 11 The lean manufacturing laws, as they were conceived at the time, are endemic in the chemical / process industry. This is highly self-limiting and also very often goes unnoticed. Obsolete plants are simply redeployed and reused, maintaining the previous physical form by only adapting the electrode chemistry or coating; the rest is attached logically, but ad hoc. The amount of fusion welding fabrication and the weights of the steel structures used are simply staggering, and in some cases, they are up to three stories high, 7 meters compared to the 2.6 meters according to existing practices. Their fitness for purpose is questionable and makes them appear as mere distractions when faced with the task of implementing hydrogen at scale in a rapidly changing world. The energy cost of air-oxygen separation is 6.6 kWh / kg. Oxygen is not typically collected as a byproduct of hydrogen generation. Therefore, a net economic benefit can be achieved by pressurizing the vessel. Decarburization in the steel industry, oxy-fuel cutting, and even fish farms are just some of the possible applications. For pressure retention, in some embodiments, the vessel comprises a composite external structure covering the polymer walls obtained by rotational molding. Thus, in some embodiments, a metal, preferably an aluminum sheet, is wound and riveted around the vessel of the invention. Preferably, at least two structural members are arranged longitudinally and vertically, reinforcing and thereby mitigating the inevitable creep of the polymer vessel under pressure. In some embodiments, a vessel of the invention includes ports for sensor level control (e.g., 3 ports), sensor pressure control (e.g., 1 port), conductivity control (e.g., 1 port), deionized water circulation (e.g., inlet and outlet, 2 ports), oxygen vent (e.g., 1 port), oxygen pressure relief (e.g., 1 port), heat exchanger (e.g., inlet and outlet, 2 ports), pump outlet (e.g., 1 port), mixed-phase return ports (x3 in a typical embodiment), and drain (e.g., 2 ports). In total, up to 17 ports are provided, representing a savings compared to the prior art. qa / οηη / ζζηζ / Ε / γίΛΐ 22 / 11 Preferably, a vessel for use in the invention includes a conical collector located below the heat exchanger. Preferably, it is connected directly to the heat exchanger. Preferably, it is constructed from a polymeric material. Figure 4 illustrates the conical collector. Element 13 is a conical collector (preferably made of polymers), which fits snugly below the heat exchanger and is connected to the inlet of the main pump, channeling and thereby increasing the velocity of the water through the heat exchanger. The pump (3) is connected to the pump outlet of the vessel and has a suction, which vigorously draws the flow through the heat exchanger, maximizing the cooling work. The homogeneity of crossflow velocities through the heat exchanger is controlled by the provided cone, which mitigates the velocity near the pump outlet port and increases the velocity (obtuse side) further from the outlet (effectively reducing longitudinal crossflow variation), and is arranged to obtain low velocity variation longitudinally through it. Alternatively, a vessel for use in the invention includes a sleeve located around the heat exchanger. This sleeve is made of polymeric material. The sleeve contains baffle plates arranged so that the fluid flow direction is crossflow around the tube, maximizing disruption of the boundary layer between the tube and the fluid to maximize heat exchange. The baffles, tube spacing, and tube length are tailored to design the pressure drop properties of the heat exchanger according to Figure 8b. Figures 5a-c show a first configuration of an oxygen separation vessel 1a. Figure 5a shows a side view of vessel 1a, Figure 5b shows an end view of vessel 1a, and Figure 5c shows a cross-sectional view of vessel 1a through section line CC. The illustrated vessel 1a has three inlet nozzles 6a, five outlet nozzles 6b, a series of parallel circumferential grooves 17, a refrigerant inlet port 18 and a refrigerant outlet port 19. Slots 17 are shaped to receive reinforcing elements such as metal reinforcing rings. These reinforcing elements provide resistance qa / on / ζζηζ / Ε / γίΛΐ 23 / 11 additional to container 1a, thus mitigating the risk of buckling of container 1a due to the high pressures exerted inside container 1a during use. As illustrated in Figures 5b and 5c, the inlet nozzles 6a are arranged at an angle (about 45 degrees in the illustrated example), so that, in use, they direct the fluid flow towards a (flat) side wall of the vessel, creating a cyclonic / centrifugal effect (as described above). As shown in Figure 5c, an internal conduit 20 is formed between the refrigerant inlet port 18 and the refrigerant outlet port 19. This internal conduit allows the flow of refrigerant through the vessel 1a and may also have additional channels that allow the flow of other fluids, such as water that has been separated from the water and oxygen mixture (these may be coupled to one or more outlet nozzles 6b). The internal conduit 20 also acts as (or houses) a heat exchanger and may have additional, unillustrated components that enable it to function as or house such a heat exchanger (as in Figure 8b). Figures 6a-d show a second configuration of a container 1b. Figure 6a shows a graphical projection of container 1b, Figure 6b shows a side view of container 1b, Figure 6c shows a bottom view of container 1b, and Figure 6d shows an end view of container 1b. Vessel 1b has three inlet nozzles 6a, five outlet nozzles 6b, two oxygen outlets 22 located on the top of vessel 1a, one coolant inlet 18, and one coolant outlet 19. Unlike vessel 1a in Figures 5a-c, vessel 1b in Figures 6a-d has no slots but rather a plurality of through-holes 21 transversely between the side walls of vessel 1b. The illustrated holes 21 are (substantially) circular in cross-section. The example vessel 1b has nine holes arranged at regular spacing, but alternative numbers of holes may be used, e.g., four, six, eight, etc. Each hole 21 is arranged to receive a reinforcing element, such as a tie rod or similar, capable of withstanding a tensile force. In use, the reinforcing elements strengthen vessel 1b against high internal pressures, thereby preventing vessel 1b from buckling or otherwise breaking / deforming. The use of through holes qa / on / z / z / z / γίΛΐ 24 / 11 instead of grooves (as in Figures 5a-c) means that the side wall of the vessel 1b can be manufactured to be smooth while maintaining the strength and integrity of the vessel 1b. Having smooth side walls is easier to manufacture than grooved side walls, so the use of through holes 21 also allows for simpler and more economical production than grooved vessels. Figures 7a-d show another alternative container 1c. The views in Figures 7a-d correspond to those in Figures 6a-d respectively. Vessel 1c is similar to that in Figures 6a-d, except that the nine circular through-holes have been replaced by six through-holes 21 having a substantially square cross-section. It should be understood that the through-holes could have other cross-sections, such as (substantially) elliptical, (substantially) rectangular, etc., and may be selected according to tooling requirements during manufacturing and / or the types of reinforcement elements to be used. Similarly, there could be more or fewer through-holes. In any case, the through-holes 21 are preferably arranged regularly to ensure a uniform load distribution across the transverse reinforcement elements. Figures 8a-d show the vessel 1b from Figures 6a-6d fitted with reinforcing elements. The views in Figures 8a-d correspond to those in Figures 6a-d respectively. The vessel 1b is provided with an external lining of sheet 23, which is preferably made of steel such as pressure steel EN 10028 P460 or equivalent. The lining 23 reinforces the vessel 1b, thereby helping to maintain the integrity of the vessel during use and mitigating the risk of buckling or similar failure. Furthermore, the vessel is provided with transverse reinforcing elements 24 received within the through-holes 21 in the form of transverse ties. These reinforcing elements 24 are preferably made of steel, and alternative transverse reinforcing elements could be used instead of ties. While the lining 23 and the transverse reinforcing elements 24 alone provide a substantial reinforcing effect, the use of the lining 23 and the transverse reinforcing elements 24 in combination further enhances the reinforcing effect because it helps to distribute the load exerted by the reinforcing elements 24 in qa / οηη / ζζηζ / E / γίΛΐ 25 / 11 the side walls of the container 1b, thus increasing the load that the container 1b can withstand before breaking or buckling. In addition to the lining 23, the vessel 1b is provided with two end plates 25, each positioned at opposite ends of the vessel 1b. The end plates 25 are connected by longitudinal reinforcing elements 26, which may also be tie rods or similar and are preferably made of steel. The longitudinal reinforcing elements 26 extend between the end plates 25 and are coupled at each end to one of the end plates 25. In this way, the end plates 25, in combination with the longitudinal reinforcing elements 26, provide strength to the vessel 1b and prevent the vessel from buckling or rupturing due to the high internal pressures experienced during use. Preferably, there are four longitudinal reinforcing elements 26, for example, coupled to each corner section of one end plate 25 to a corresponding corner section of the opposite end plate 25. The 25 end plates are preferably made of steel, such as EN10028 P460 pressure steel or equivalent. Although the lining 23, the reinforcing elements 24, 26, and the end plates 25 have been described in relation to the vessel 1b illustrated in Figures 6a-d, they could also be used with other vessels, such as the one shown in Figures 7a-d. The use of transverse ties 24 requires that the vessel have through-holes 21, but the lining and end plates can be used with vessels that do not have through-holes. Alternatively, the shell shapes of rolled steel or aluminum could be replaced by semi-cylindrical shell shapes of fiberglass (to respond to the stresses of lightness and tension in the circular parts of the vessel), while the side walls (subjected to bending stresses) could be made of ductile steel or aluminum. Figures 5a-c, 6a-d, 7a-d, and 8a-d are technical drawings and show the container to scale; that is, the proportions in the drawings are accurate. All dimensions given in these figures are in millimeters (mm). The dimensions illustrated in these figures are preferred values ​​but should not be interpreted as limiting unless otherwise stated in the claims. qa / οηη / ζζηζ / Ε / γίΛΐ 26 / 11 It should be understood that the number of inlet nozzles 6a in any of the examples above could vary. While the examples show three, there could alternatively be one, two, four, or more nozzles. However, having more than one inlet nozzle is preferred because this leads to the creation of multiple columns of the mixture within the vessel, which greatly improves the separation rate for a given vessel height, allowing the vessel to be much shorter than conventional oxygen separation vessels. Although not all of the illustrative containers are shown with an oxygen outlet 22, it should be understood that this has been omitted to simplify the drawings and that each of the containers is intended to have at least one oxygen outlet. Any of the containers in Figures 5a-c, 6a-d, 7a-d and 8a-d could be used in combination with the system described above with reference to Figures 1-4. The vessel may be referred to interchangeably as a gas separation vessel or an oxygen separation vessel. Preferred embodiments of the vessel are as an oxygen separation vessel for separating oxygen from a mixture containing oxygen and water (particularly in the context of green hydrogen generation from renewable electricity), but the separation of other gases from other mixtures is also possible. Generally, oxygen and water will be separated in different stages due to the unstable / volatile nature of oxygen / hydrogen mixtures.

Claims

1. A system comprising a stack of electrolyzers connected to a water / gas separation vessel, via inlet and outlet pipes, wherein: the separation vessel is adapted to passively separate water and gas; the separation vessel contains a heat exchanger; and the separation vessel is constructed of a polymeric material.

2. A system according to claim 1, wherein the separation vessel comprises a plurality of nozzles for connecting each of the inlet and outlet pipes, wherein the nozzles are integral with the vessel and are constructed of the same polymeric material as the vessel.

3. A system according to claim 2, wherein the container comprises at least 4 nozzles, with at least 2 nozzles adapted to be in fluid communication with each pipe.

4. A system according to claim 2 or claim 3, comprising at least 6 nozzles, wherein at least 3 nozzles are adapted to be in fluid communication with each pipe.

5. A system according to any of the preceding claims, wherein the container is rotationally molded in a single one-step process from the polymeric material.

6. A system according to any of the preceding claims, wherein the pipes are constructed from a polymeric material. qa / on / zzzz / E / γίΛΐ 28 / 11 7. A system according to any of claims 2 to 6, wherein the nozzles are connected to the pipes by polymer fusion.

8. A system according to any of the preceding claims, wherein the container has a flat oval cross-section, the flat side walls being positioned vertically in use.

9. A system according to claim 8, wherein the nozzles are positioned so that, in use, they direct the fluid flow towards a flat side wall of the container, thereby creating a cyclonic effect.

10. A system according to any of claims 2 to 9, wherein a wire brush is located within at least one nozzle, so that the kinetic energy of a fluid stream is interrupted during use.

11. A system according to any of claims 2 to 10, wherein a vortex switch, a vortex deflector or an anti-fog pad are located within at least one first tube.

12. A system according to any of the preceding claims, wherein the proportions of the container are such that the ratio of the height to the width of the container is less than 3:1 or 2:1, or preferably about 1:

1.

13. A system according to any of the preceding claims, wherein the container comprises an antibacterial or antifungal additive.

14. A system according to any of the preceding claims, wherein the heat exchanger is a tube heat exchanger.

15. A system according to any of the preceding claims, wherein the heat exchanger is adapted to use water, for example, seawater, as a coolant. qa / onοηη / ζζηζ / E / γίΛΐ 29 / 11 16. A system according to any of the preceding claims, wherein at least one pipe includes a pump to allow fluid flow around the system in use, and preferably wherein the pump is located in the pipe flowing from the vessel to the stack.

17. A system according to claim 16, wherein the pump is a centrifugal pump.

18. A system according to any of the preceding claims, wherein the vessel includes ports for sensor level control, sensor pressure control, conductivity control, deionized water circulation, oxygen pressure relief and / or connection to and from the heat exchanger, preferably wherein these ports are an integral part of the vessel and more preferably constructed from the same polymeric material as the vessel and preferably manufactured by injection molding or single-action rotational molding.

19. A system according to any of the preceding claims, wherein there is a conical collector located between the heat exchanger and an outlet pipe of the vessel, such that the fluid flow velocity towards the outlet pipe increases during use.

20. A method for electrolyzing water using the system according to any of the preceding claims, wherein the gas / water separation vessel contains water, and wherein the electrolyzer electrolyzes the water to produce hydrogen and oxygen, which then flow through a pipe to the separation vessel, where both the hydrogen and oxygen are passively separated from the water and extracted from the system.

21. An oxygen separation vessel for passively separating water from an oxygen and water mixture, the vessel comprising: a plurality of inlet nozzles for receiving the oxygen and water mixture; a heat exchanger positioned within the vessel for cooling the oxygen and water mixture; at least one oxygen outlet for discharging oxygen separated from the oxygen and water mixture; and at least one water outlet nozzle for discharging water separated from the oxygen and water mixture.

22. The oxygen separation vessel of claim 21, wherein the vessel is constructed from a polymeric material.

23. The oxygen separation vessel of claim 21 of claim 22, wherein the inlet nozzles are located on or near the top of the oxygen separation vessel.

24. The oxygen separation vessel of any of claims 21 to 23, further comprising at least one through-hole for receiving a transverse reinforcing element, preferably wherein at least one through-hole has a substantially rectangular or substantially elliptical cross-section, 25. The oxygen separation vessel of claim 24, further comprising a transverse reinforcing element received in at least one through hole.

26. The oxygen separation vessel of any of claims 21 to 25, further comprising an external sheet lining. qa / on / zzzz / E / γίΛΐ 31 / 11 27. The oxygen separation vessel of claim 26, wherein the outer sheet lining is made of steel.

28. The oxygen separation vessel of any of claims 21 to 23, wherein the vessel comprises at least one circumferential groove for receiving a circumferential reinforcing element.

29. The oxygen separation vessel of any of claims 21 to 28, further comprising two external end plates arranged at opposite ends of the vessel, wherein the external end plates are coupled by one or more longitudinal reinforcing elements.

30. The oxygen separation vessel of claim 29, wherein the end plate is made of steel.

31. The oxygen separation vessel of any of claims 21 to 29, wherein the plurality of inlet nozzles and at least one water outlet nozzle are an integral part of the vessel and are constructed of the same material as the vessel, preferably wherein the nozzles are connected to the pipes by polymer fusion.

32. The oxygen separation vessel of any of claims 21 to 30, wherein the plurality of inlet nozzles are located substantially at the same height.

33. The oxygen separation vessel of any of claims 21 to 32, wherein the vessel is rotationally molded in a single one-step process. qa / on / zzzz / E / γίΛΐ 32 / 11 34. The oxygen separation vessel of any of claims 21 to 33, wherein the vessel has a flat oval cross-section, with vertically positioned flat side walls, in use.

35. The oxygen separation vessel of claim 34, wherein the inlet nozzles are positioned so that, in use, they direct the fluid flow towards a flat side wall of the vessel, so as to create a cyclone effect.

36. The oxygen separation vessel of any of claims 21 to 34, wherein the inlet nozzles are positioned so that, in use, they direct the fluid flow along the curvature of a side wall of the vessel and towards an opposite side wall.

37. The oxygen separation vessel of any of claims 21 to 36, wherein the vessel is constructed of high-performance hexane high-density polyethylene.

38. The oxygen separation vessel of any of claims 21 to 37, further comprising a conical collector located between the heat exchanger and at least one water outlet nozzle.

39. The oxygen separation vessel of any of claims 21 to 38, wherein the heat exchanger is a tubular heat exchanger.

40. The oxygen separation vessel of claim 39, further comprising a sleeve arranged around the tubular heat exchanger, preferably wherein the sleeve is made of polymeric material.

41. The oxygen separation vessel of claim 40, wherein the sleeve comprises an inlet, an outlet and one or more baffle plates arranged to cause the fluid to flow in a cross-flow direction around the heat exchanger when in use.

42. A system for generating hydrogen, comprising a stack of 5 electrolyzers connected to the oxygen separation vessel of any of claims 21-41.

43. The system of claim 42, further comprising a pump connected to at least one water outlet nozzle, wherein the pump is located 10 downstream of the oxygen separation vessel.

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