Gas-liquid separation system for hydrogen production by alkaline water electrolysis

Abstract

The application relates to the field of hydrogen production by water electrolysis, and discloses a gas-liquid separation system for hydrogen production by alkaline water electrolysis, which comprises an electrolytic tank, a hydrogen-alkali gas-liquid separator, an oxygen-alkali gas-liquid separator, a first circulating pump, an alkali solution cooler, a filter, an alkali solution flowmeter, at least one alkali solution buffer tank, a second circulating pump and a plurality of pipeline assemblies; the liquid outlets of the electrolytic tank are respectively communicated with the inlets of the hydrogen-alkali gas-liquid separator and the oxygen-alkali gas-liquid separator through the pipeline assemblies; and the liquid outlets of the hydrogen-alkali gas-liquid separator and the oxygen-alkali gas-liquid separator are respectively communicated with the inlet of the first circulating pump through the pipeline assemblies. The alkali solution in the gas-liquid separator is discharged to the alkali solution buffer tank, the tiny gas bubbles are rapidly expanded and escaped by pressure drop, the ultrasonic coalescence of an ultrasonic wave release device or an ultrasonic device is used, the gas content in the alkali solution circulating back to the electrolytic tank is reduced, the internal resistance of the electrolytic tank is reduced, the energy consumption of the electrolytic hydrogen production is reduced, and the purity of hydrogen and oxygen is improved.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production technology by water electrolysis, specifically to a gas-liquid separation system for hydrogen production by alkaline water electrolysis. Background Technology

[0002] In a conventional gas-liquid separation system, the hydrogen (oxygen) alkali gas-liquid separator is the core. When the gas and liquid two-phase flow enters the separator, the gas and liquid are separated due to density differences and gravity. The liquid remains in the container for a period of time before flowing out and returning to the electrolytic cell via an alkali circulation pump to complete the cycle. The gas escapes to the surface of the liquid as bubbles, resisting the viscosity of the liquid, thus achieving gas-liquid separation.

[0003] However, due to the uneven distribution of bubble size in the two-phase flow, small bubbles have less buoyancy and are insufficient to escape to the surface and complete separation within the short residence time. When these bubbles flow back to the electrolyzer with the alkaline solution, they not only increase the resistance within the electrolyzer to some extent but also negatively impact the purity of the gas output from the electrolyzer. Therefore, to achieve better separation results in this gas-liquid separation system, it is often necessary to increase the separator volume to extend the liquid residence time, allowing bubbles more time to escape. However, increasing the container volume significantly increases container costs, while the separation effect gain is relatively low, resulting in poor cost-effectiveness.

[0004] Therefore, finding a gas-liquid separation system with better gas separation performance to improve gas purity and reduce electrolytic cell energy consumption has become one of the problems that need to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a gas-liquid separation system for hydrogen production via alkaline water electrolysis, which solves the problem that microbubbles are difficult to remove effectively in existing alkaline water electrolysis hydrogen production gas-liquid separation systems, leading to increased internal resistance of the electrolyzer, increased energy consumption, and decreased gas purity.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a gas-liquid separation system for producing hydrogen by alkaline water electrolysis, comprising an electrolyzer, a hydrogen-alkali gas-liquid separator, an oxygen-alkali gas-liquid separator, a first circulating pump, an alkaline cooler, a filter, an alkaline flow meter, at least one alkaline buffer tank, a second circulating pump, and multiple pipeline components. The outlet of the electrolytic cell is connected to the inlet of the hydrogen-alkali gas-liquid separator and the inlet of the oxygen-alkali gas-liquid separator respectively through a pipeline assembly; The outlet of the hydrogen-alkali gas-liquid separator and the outlet of the oxygen-alkali gas-liquid separator are respectively connected to the inlet of the first circulating pump through a pipeline assembly. The outlet of the first circulating pump is connected in sequence to the alkali cooler, the filter, the alkali flow meter and the inlet of the electrolytic cell via a pipeline assembly; The outlet of the hydrogen-alkali gas-liquid separator and / or the outlet of the oxygen-alkali gas-liquid separator are also connected to the inlet of the alkali buffer tank through a pipeline assembly. The outlet of the alkali buffer tank is connected to the inlet of the second circulation pump through a pipeline assembly. The outlet of the second circulation pump is connected to the inlet of the hydrogen-alkali gas-liquid separator and / or the inlet of the oxygen-alkali gas-liquid separator through a pipeline assembly, or connected to the inlet of the electrolytic cell. The alkaline buffer tank is an atmospheric pressure vessel or a negative pressure vessel; the interior of the alkaline buffer tank is provided with baffles and / or a three-dimensional porous filling skeleton; and an ultrasonic device is provided inside or outside the alkaline buffer tank.

[0007] Preferably, an ultrasonic release device is provided on the pipeline assembly between the outlet of the second circulating pump and the inlet of the hydrogen-alkali gas-liquid separator and / or the inlet of the oxygen-alkali gas-liquid separator.

[0008] Preferably, the alkaline buffer tank is provided with a gas-liquid two-phase flow inlet, and a fluid distributor and a diffuser are configured at the gas-liquid two-phase flow inlet.

[0009] Preferably, a liquid discharge valve is provided on the pipeline assembly between the outlet of the hydrogen-alkali gas-liquid separator and the alkali buffer tank and / or on the pipeline assembly between the outlet of the oxygen-alkali gas-liquid separator and the alkali buffer tank.

[0010] Preferably, the alkali buffer tank is a single unit, and one of the outlets of the hydrogen-alkali gas-liquid separator and the oxygen-alkali gas-liquid separator is connected to the inlet of the alkali buffer tank via a pipeline assembly.

[0011] Preferably, there are two alkali buffer tanks, including a first buffer tank and a second buffer tank; The outlet of the hydrogen-alkali gas-liquid separator is connected to the inlet of the first buffer tank via a pipeline assembly, and the outlet of the oxygen-alkali gas-liquid separator is connected to the inlet of the second buffer tank via a pipeline assembly; the outlets of the first buffer tank and the second buffer tank are connected to the inlet of the second circulating pump via a pipeline assembly.

[0012] Preferably, the outlet of the second circulating pump is connected in sequence to the alkali cooler, the filter, the alkali flow meter, and the inlet of the electrolytic cell via a pipeline assembly.

[0013] Working principle: During electrolysis, the generated hydrogen / alkali two-phase flow mixture and oxygen / alkali two-phase flow mixture enter the hydrogen-alkali gas-liquid separator and the oxygen-alkali gas-liquid separator, respectively. Under gravity, hydrogen or oxygen escapes upward and is discharged through the gas outlet, while the alkali settles at the bottom of the separator. The alkali settled at the bottom of the separator is then pumped sequentially by the first circulation pump to the alkali cooler, filter, and alkali flow meter, and finally returned to the electrolyzer, forming the main circulation loop for the alkali.

[0014] Because conventional gas-liquid separators operate at high pressures, tiny bubbles cannot completely escape. This system uses a liquid drain valve to release a portion of the alkaline solution from the separator to an alkaline buffer tank, utilizing the pressure drop to cause the tiny bubbles to rapidly expand and escape. The alkaline buffer tank is an atmospheric or negative pressure vessel, and its interior can be equipped with baffles, a three-dimensional porous packing structure, a fluid distributor, diffusers, and an ultrasonic device. Through multiple mechanisms such as extending the flow path, intercepting and coalescing bubbles, and ultrasonic cavitation, the degassing effect is further enhanced. The degassed alkaline solution is pumped out by a second circulation pump, and depending on the design, there are three possible return paths: Option 1: An alkali buffer tank is used, into which either the hydrogen-side or oxygen-side alkali solution is degassed. An ultrasonic release device is installed at the outlet of the second circulation pump. After degassed alkali solution passes through the ultrasonic release device to further coalesce microbubbles, it returns to the hydrogen-alkali gas-liquid separator and / or the oxygen-alkali gas-liquid separator to dilute the gas content of the alkali solution inside the separator, and finally returns to the electrolyzer through the main circulation loop.

[0015] Option 2: Two independent alkali buffer tanks are used. The alkali solution from the hydrogen side enters the first buffer tank, and the alkali solution from the oxygen side enters the second buffer tank. Degassing is performed independently on both sides. The outlets of the two buffer tanks are combined and connected to a second circulation pump. The degassed alkali solution is returned to the hydrogen-alkali gas-liquid separator and / or the oxygen-alkali gas-liquid separator. This option allows for independent control of the degassing process based on the different operating conditions of the hydrogen and oxygen sides. An ultrasonic release device is optional.

[0016] Option 3: Two independent alkali buffer tanks are used. The hydrogen-side and oxygen-side alkali solutions enter their respective buffer tanks for degassing. The buffer tanks are equipped with optimized structures such as baffles, a three-dimensional porous packing framework, a fluid distributor, a diffuser, and an ultrasonic device. The outlets of the two buffer tanks are combined and connected to a second circulation pump. The degassed alkali solution does not return to the separator, but is directly returned to the electrolyzer via an alkali cooler, filter, and alkali flow meter, allowing the degassed alkali solution to enter the electrolyzer more quickly.

[0017] This invention provides a gas-liquid separation system for hydrogen production via alkaline water electrolysis. It offers the following advantages: 1. This invention releases the alkaline solution from the gas-liquid separator into an alkaline buffer tank. The pressure drop causes tiny bubbles to rapidly expand and escape. Simultaneously, the alkaline buffer tank is designed as an atmospheric or negative pressure vessel to maximize the pressure drop effect. Baffles and / or a three-dimensional porous filling framework inside the tank extend the flow path of the alkaline solution, intercepting and coalescing the bubbles. An ultrasonic device inside or outside the tank generates ultrasonic cavitation, further promoting bubble collision and coalescence. These three mechanisms—pressure release degassing, physical interception degassing, and ultrasonic-assisted degassing—work synergistically within the same alkaline buffer tank, significantly reducing the gas content in the alkaline solution circulating back to the electrolyzer. This effectively reduces the internal resistance of the electrolyzer and significantly lowers the energy consumption for hydrogen production through electrolysis.

[0018] 2. This invention significantly reduces the gas content in the alkali solution circulating back to the electrolyzer, preventing hydrogen bubbles carried in the alkali solution from entering the oxygen side of the electrolyzer and interfering with oxygen purity, and also preventing oxygen bubbles carried in the alkali solution from entering the hydrogen side of the electrolyzer and interfering with hydrogen purity. At the same time, by setting up independent hydrogen-side alkali solution buffer tanks and oxygen-side alkali solution buffer tanks, cross-mixing of the alkali solutions on both the hydrogen and oxygen sides is avoided, thereby effectively improving the purity of hydrogen and oxygen.

[0019] 3. Without increasing the volume of the original gas-liquid separator, this invention achieves better gas-liquid separation effect at a lower cost by adding an alkaline buffer tank and a second circulation pump and other auxiliary degassing circuits, which has high cost performance and industrial applicability. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the gas-liquid separation system in Scheme 1 of the present invention; Figure 2 This is a schematic diagram of the gas-liquid separation system in Scheme 2 of the present invention; Figure 3 This is a schematic diagram of the gas-liquid separation system in Scheme 3 of the present invention; Figure 4 This is a schematic diagram of the internal structure of the alkali buffer tank of the present invention.

[0021] The components include: 1. Electrolytic cell; 2. Liquid drain valve; 3. Oxy-alkali gas-liquid separator; 4. Hydrogen-alkali gas-liquid separator; 5. First circulation pump; 6. Alkali cooler; 7. Filter; 8. Alkali flow meter; 9. Alkali buffer tank; 10. Second circulation pump; 11. Ultrasonic release device; 12. Diffuser; 13. Gas-liquid two-phase inlet; 14. Three-dimensional porous filled skeleton; and 15. Baffle plate. Detailed Implementation

[0022] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please see the appendix Figure 1 - Appendix Figure 4 This invention provides a gas-liquid separation system for hydrogen production via alkaline water electrolysis, comprising an electrolytic cell 1, a hydrogen-alkali gas-liquid separator 4, an oxygen-alkali gas-liquid separator 3, a first circulating pump 5, an alkali cooler 6, a filter 7, an alkali flow meter 8, at least one alkali buffer tank 9, a second circulating pump 10, and multiple piping assemblies. The outlet of electrolytic cell 1 is connected to the inlet of hydrogen-alkali gas-liquid separator 4 and the inlet of oxygen-alkali gas-liquid separator 3 respectively through a pipeline assembly. The outlet of the hydrogen-alkali gas-liquid separator 4 and the outlet of the oxygen-alkali gas-liquid separator 3 are respectively connected to the inlet of the first circulating pump 5 through a pipeline assembly. The outlet of the first circulating pump 5 is connected in sequence to the alkali cooler 6, the filter 7, the alkali flow meter 8 and the inlet of the electrolytic cell 1 through a pipeline assembly. The outlet of the hydrogen-alkali gas-liquid separator 4 and / or the outlet of the oxygen-alkali gas-liquid separator 3 are also connected to the inlet of the alkali buffer tank 9 through a pipeline assembly. The outlet of the alkali buffer tank 9 is connected to the inlet of the second circulation pump 10 through a pipeline assembly. The outlet of the second circulation pump 10 is connected to the inlet of the hydrogen-alkali gas-liquid separator 4 and / or the inlet of the oxygen-alkali gas-liquid separator 3 through a pipeline assembly, or to the inlet of the electrolytic cell 1.

[0024] Specifically, the outlet of electrolytic cell 1 is connected to the inlet of hydrogen-alkali gas-liquid separator 4 and the inlet of oxygen-alkali gas-liquid separator 3 via a piping assembly. During operation, electrolytic cell 1 outputs a two-phase mixture of hydrogen and alkali solution, and a two-phase mixture of oxygen and alkali solution, respectively, through two pipelines. The hydrogen-alkali solution mixture enters hydrogen-alkali gas-liquid separator 4, while the oxygen-alkali solution mixture enters oxygen-alkali gas-liquid separator 3. The outlets of hydrogen-alkali gas-liquid separator 4 and oxygen-alkali gas-liquid separator 3 are connected to the inlet of the first circulation pump 5 via piping assemblies. Hydrogen-alkali gas-liquid separator 4 and oxygen-alkali gas-liquid separator 3 perform preliminary gas-liquid separation of their internal gas-liquid two-phase flows, with the separated alkali solution flowing out of their respective outlets and converging into the first circulation pump 5.

[0025] The outlet of the first circulation pump 5 is connected sequentially to the alkali cooler 6, filter 7, alkali flow meter 8, and the inlet of the electrolytic cell 1 via a pipeline assembly. The first circulation pump 5 pumps the alkali solution to the alkali cooler 6 for cooling. The cooled alkali solution is then filtered by the filter 7, and after the flow rate is measured by the alkali flow meter 8, it returns to the electrolytic cell 1, completing the main circulation loop of the alkali solution. The outlet of the hydrogen-alkali gas-liquid separator 4 and / or the outlet of the oxygen-alkali gas-liquid separator 3 are also connected to the inlet of the alkali buffer tank 9 via a pipeline assembly. Specifically, a liquid drain valve 2 can be installed on the pipeline assembly between the outlet of the hydrogen-alkali gas-liquid separator 4 and the alkali buffer tank 9, and / or on the pipeline assembly between the outlet of the oxygen-alkali gas-liquid separator 3 and the alkali buffer tank 9. By controlling the opening of the liquid drain valve 2, a portion of the alkali solution in the hydrogen-alkali gas-liquid separator 4 and / or the oxygen-alkali gas-liquid separator 3 is drained into the alkali buffer tank 9.

[0026] The outlet of the alkali buffer tank 9 is connected to the inlet of the second circulation pump 10 via a piping assembly. The alkali buffer tank 9 is an atmospheric pressure or negative pressure vessel. When pressurized alkali enters the alkali buffer tank 9, the pressure drops, causing the tiny bubbles entrained in the alkali to rapidly expand and escape, achieving initial bubble removal. The outlet of the second circulation pump 10 is connected to the inlet of the hydrogen-alkali gas-liquid separator 4 and / or the inlet of the oxygen-alkali gas-liquid separator 3 via a piping assembly, or to the inlet of the electrolytic cell 1. After degassing in the alkali buffer tank 9, the alkali is pumped back to the hydrogen-alkali gas-liquid separator 4 and / or the oxygen-alkali gas-liquid separator 3 by the second circulation pump 10 to dilute the gas content of the alkali inside the separator; or it is directly pumped back to the electrolytic cell 1 to reduce the residence time of the alkali in the circulation path.

[0027] In a preferred embodiment, an ultrasonic release device 11 is provided on the pipeline assembly between the outlet of the second circulation pump 10 and the inlet of the hydrogen-alkali gas-liquid separator 4 and / or the inlet of the oxygen-alkali gas-liquid separator 3. The ultrasonic waves generated by the ultrasonic release device 11 act on the flowing alkali solution, causing the residual microbubbles in the alkali solution to coalesce into larger bubbles with stronger buoyancy, thus making it easier for them to detach from the liquid phase.

[0028] In another preferred embodiment, the interior of the alkali buffer tank 9 is provided with baffles 15 and / or a three-dimensional porous packing skeleton 14. The baffles 15 can be installed vertically or at an angle to extend the flow path of the alkali solution within the alkali buffer tank 9 and increase the time for bubble detachment. The three-dimensional porous packing skeleton 14 is used to intercept, adhere to, and secondary coalesce bubbles in the alkali solution, while simultaneously disrupting the entrainment state of bubbles in the flow channel, making it easier for bubbles to detach from the liquid phase and discharge upwards.

[0029] In another preferred embodiment, the alkali buffer tank 9 is provided with a gas-liquid two-phase flow inlet 13, and a fluid distributor and a diffuser 12 are arranged at the gas-liquid two-phase flow inlet 13. After being evenly distributed by the fluid distributor and the diffuser 12, the gas-liquid two-phase flow enters the interior of the alkali buffer tank 9, which increases the gas-liquid contact area and is beneficial to the initial release of bubbles.

[0030] In another preferred embodiment, an ultrasonic device is provided inside or outside the alkali buffer tank 9. The ultrasonic device can be integrated with the alkali buffer tank 9 to apply ultrasonic action to the alkali solution inside the tank, further promoting the coalescence and detachment of bubbles.

[0031] Regarding the quantity configuration of the alkali buffer tanks 9, this application provides the following two specific implementation methods: In one embodiment, there is one alkali buffer tank 9. The outlet of either the hydrogen-alkali gas-liquid separator 4 or the outlet of the oxygen-alkali gas-liquid separator 3 is connected to the inlet of the alkali buffer tank 9 via a piping assembly. Either the hydrogen-side alkali solution or the oxygen-side alkali solution enters the alkali buffer tank 9 for degassing.

[0032] In another embodiment, there are two alkali buffer tanks 9, including a first buffer tank and a second buffer tank. The outlet of the hydrogen-alkali gas-liquid separator 4 is connected to the inlet of the first buffer tank via a piping assembly, and the outlet of the oxygen-alkali gas-liquid separator 3 is connected to the inlet of the second buffer tank via a piping assembly. The outlets of the first and second buffer tanks are combined via a piping assembly and connected to the inlet of the second circulating pump 10. The hydrogen-side alkali solution and the oxygen-side alkali solution enter separate alkali buffer tanks 9 for degassing treatment, further reducing the risk of cross-contamination.

[0033] In another specific implementation, the outlet of the second circulation pump 10 is connected sequentially to the alkali cooler 6, filter 7, alkali flow meter 8, and the inlet of the electrolytic cell 1 via a piping assembly. In this embodiment, the alkali solution, after degassing in the alkali buffer tank 9, is directly pumped by the second circulation pump 10 to the alkali cooler 6, filter 7, and alkali flow meter 8, and then returned to the electrolytic cell 1, without passing through the hydrogen-alkali gas-liquid separator 4 or the oxygen-alkali gas-liquid separator 3. This method shortens the circulation path of the alkali solution, allowing the degassed "clean" alkali solution to enter the electrolytic cell 1 more quickly.

[0034] The technical features described in the above embodiments can be combined with each other, as long as such combination does not create contradictions or become impossible. Those skilled in the art should understand that, depending on actual operating conditions and degassing requirements, one or more of the above embodiments can be selected for combination and configuration.

[0035] Please see the appendix Figure 1 -Appendix Figure 3A liquid discharge valve 2 is provided on the pipeline assembly between the outlet of the hydrogen-alkali gas-liquid separator 4 and the alkali buffer tank 9, and / or on the pipeline assembly between the outlet of the oxygen-alkali gas-liquid separator 3 and the alkali buffer tank 9.

[0036] Specifically, the liquid discharge valve 2 can be an electric or pneumatic regulating valve, and its opening degree is continuously adjusted by the control system based on the liquid level signal inside the hydrogen-alkali gas-liquid separator 4 and / or the oxygen-alkali gas-liquid separator 3. When the liquid level inside the hydrogen-alkali gas-liquid separator 4 and / or the oxygen-alkali gas-liquid separator 3 rises, the control system increases the opening degree of the liquid discharge valve 2, allowing more alkali solution to be discharged into the alkali buffer tank 9; when the liquid level drops, the control system decreases the opening degree of the liquid discharge valve 2, reducing the discharge amount accordingly; the valve is usually kept in a certain open state, not completely closed, to maintain a stable discharge and degassing process.

[0037] By setting up the liquid discharge valve 2, precise control of the alkaline solution discharge rate can be achieved, preventing excessive discharge from causing the liquid level inside the hydrogen-alkali gas-liquid separator 4 or the oxygen-alkali gas-liquid separator 3 to be too low, thus affecting the gas-liquid separation effect; at the same time, it can also prevent insufficient degassing effect due to insufficient discharge. The opening frequency and opening duration of the liquid discharge valve 2 can be adjusted according to the actual working conditions. For example, when the working load of the electrolytic cell 1 is high and the gas production is large, the discharge frequency can be appropriately increased or the discharge duration can be extended to send more alkaline solution into the alkaline solution buffer tank 9 for degassing treatment.

[0038] In embodiments where liquid relief valves 2 are installed on both the pipeline assembly between the outlet of the hydrogen-alkali gas-liquid separator 4 and the alkali buffer tank 9, and on both the pipeline assembly between the outlet of the oxygen-alkali gas-liquid separator 3 and the alkali buffer tank 9, the two liquid relief valves 2 are typically controlled synchronously with consistent opening degrees to maintain stable system operation and avoid coupling with the gas pipeline regulating valve. Based on the overall liquid levels on both the hydrogen and oxygen sides, the opening degrees of the two valves can be adjusted simultaneously. For example, when both liquid levels are high, the opening degree is increased simultaneously to increase the relief amount; when both liquid levels are low, the opening degree is decreased simultaneously to reduce the relief amount. The two liquid relief valves 2 are generally kept in a certain open state, not completely closed.

[0039] To prevent potential safety hazards, the system can also take the following safety measures: a one-way valve is installed on the pipeline between the outlet of the second circulation pump 10 and the inlet of the hydrogen-alkali gas-liquid separator 4 and / or the inlet of the oxygen-alkali gas-liquid separator 3 to prevent alkali backflow; a flame arrester should be installed at the vent of the alkali buffer tank 9 to prevent backfire; and gas concentration monitoring sensors are installed at appropriate locations to monitor the hydrogen and oxygen concentrations in the pipeline in real time. When the gas concentration monitoring sensor detects that the hydrogen or oxygen concentration exceeds the preset safety threshold, the control system issues an alarm signal and automatically closes the liquid drain valve 2 and the second circulation pump 10, while simultaneously cutting off the system power supply to ensure system safety.

[0040] The valve body material of liquid relief valve 2 should be made of alkali-resistant material, such as 316L stainless steel or Hastelloy, to meet the corrosive requirements of strongly alkaline liquids in the alkaline water electrolysis hydrogen production environment. The sealing element of liquid relief valve 2 should be made of alkali-resistant, temperature-resistant, and pressure-resistant elastic material, such as polytetrafluoroethylene or perfluoroether rubber, to ensure long-term sealing reliability.

[0041] By setting and controlling the liquid discharge valve 2, this system can controllably discharge the alkaline solution containing tiny bubbles from the hydrogen-alkali gas-liquid separator 4 and / or the oxygen-alkali gas-liquid separator 3 into the alkaline solution buffer tank 9. The pressure change causes the bubbles to expand and escape, thereby effectively reducing the gas content of the alkaline solution.

[0042] Please refer to the appendix. Figure 1 An ultrasonic release device 11 is installed on the pipeline assembly between the outlet of the second circulation pump 10 and the inlet of the hydrogen-alkali gas-liquid separator 4 and / or the inlet of the oxygen-alkali gas-liquid separator 3.

[0043] Specifically, the ultrasonic releaser 11 applies ultrasonic waves to the alkaline solution transported by the second circulation pump 10. When the ultrasonic waves propagate in the alkaline solution, they generate cavitation and mechanical vibration, causing residual microbubbles in the solution to collide and coalesce, forming larger bubbles with stronger buoyancy. These larger, coalesced bubbles are more easily detached from the liquid phase and can return to the alkaline buffer tank 9 via pipeline, or enter the hydrogen-alkali gas-liquid separator 4 or the oxygen-alkali gas-liquid separator 3 with the alkaline solution, where they can quickly rise above the liquid surface to complete separation. The operating frequency of the ultrasonic releaser 11 can be adjusted according to the size distribution of the bubbles in the alkaline solution. For alkaline solutions containing a large number of submicron-sized microbubbles, higher frequencies, such as 40kHz-80kHz, are beneficial for enhancing the cavitation effect; for alkaline solutions with relatively large bubbles, lower frequencies, such as 20kHz-40kHz, can obtain larger cavitation bubbles and enhance the mechanical vibration effect. In practical applications, a frequency conversion control method can be used to adjust the operating frequency and power of the ultrasonic releaser 11 in real time according to the degassing effect.

[0044] The ultrasonic release device 11 can be configured as one or more. When multiple ultrasonic release devices 11 are configured, they can be arranged sequentially along the axial direction of the pipeline assembly to form a multi-stage ultrasonic treatment zone, allowing the alkaline solution to pass through multiple ultrasonic fields sequentially, further enhancing the bubble coalescence effect. Multiple ultrasonic release devices 11 can operate at the same frequency or different frequencies to cover a wider range of bubble sizes. To prevent the ultrasonic release device 11 from generating electrical sparks and causing safety hazards in hydrogen or oxygen environments, the ultrasonic release device 11 should adopt an explosion-proof design, with an enclosure protection rating of not less than IP65, and comply with relevant standards for electrical equipment used in explosive gas atmospheres. The transducer oscillator of the ultrasonic release device 11 should be made of alkali-resistant materials, such as titanium alloy or stainless steel, to ensure a long service life in alkaline environments.

[0045] It should be noted that the ultrasonic release device 11 is an optional component. In practical applications, if the degassing effect of the alkali buffer tank 9 is sufficient to meet the process requirements, the ultrasonic release device 11 may not be necessary; however, if a higher gas content in the alkali solution is required, the ultrasonic release device 11 can be added to enhance the degassing effect. This modular design allows the system to be flexibly configured according to actual needs, achieving a balance between cost and effectiveness.

[0046] Through the ultrasonic coalescence effect of the ultrasonic releaser 11, tiny bubbles in the alkali solution are effectively removed, further reducing the gas content of the alkali solution circulating back to the electrolytic cell 1, thereby reducing the internal resistance of the electrolytic cell 1, reducing electrolysis energy consumption, and avoiding the influence of bubbles on gas purity.

[0047] Please see the appendix Figure 1 - Appendix Figure 4 The alkali buffer tank 9 is an atmospheric pressure vessel or a negative pressure vessel. The interior of the alkali buffer tank 9 is equipped with baffles 15 and / or a three-dimensional porous packed skeleton 14. The alkali buffer tank 9 is provided with a gas-liquid two-phase flow inlet 13, at which a fluid distributor and a diffuser 12 are installed. An ultrasonic device is installed inside or outside the alkali buffer tank 9.

[0048] Specifically, when the alkali buffer tank 9 is an atmospheric pressure vessel, its internal pressure is essentially equal to atmospheric pressure. Pressurized alkali solution from the hydrogen-alkali gas-liquid separator 4 or the oxygen-alkali gas-liquid separator 3 enters the atmospheric pressure alkali buffer tank 9 through the liquid relief valve 2. The pressure drops sharply, causing tiny bubbles entrained in the alkali solution to rapidly expand and escape due to the pressure drop, achieving initial bubble removal. When the alkali buffer tank 9 is a negative pressure vessel, its internal pressure is lower than atmospheric pressure. An external vacuum pump or suction device maintains a negative pressure inside the alkali buffer tank 9. The pressure drop is even greater after the pressurized alkali solution enters, resulting in more complete bubble expansion and further enhanced degassing. Negative pressure vessels are suitable for applications requiring extremely high alkali solution gas content.

[0049] Baffles 15 are installed vertically or at an angle inside the alkali buffer tank 9. After entering the alkali buffer tank 9, the alkali flows along a tortuous path under the guidance of baffles 15, effectively prolonging the residence time of the alkali in the tank and increasing the chance of bubbles escaping from the liquid phase. At the same time, baffles 15 turbulent the alkali, promoting bubble coalescence and buoyancy. A three-dimensional porous packed skeleton 14 is set inside the alkali buffer tank 9, and its material is a porous material resistant to alkali corrosion, such as nickel foam, porous ceramic, or metal wire mesh. When the alkali flows through the three-dimensional porous packed skeleton 14, the bubbles in the alkali are intercepted and attached by the porous structure of the skeleton. At the same time, the bubbles undergo secondary coalescence on the surface of the skeleton, forming larger bubbles that detach from the skeleton and are discharged upwards. The three-dimensional porous packed skeleton 14 can also disrupt the entrainment state of bubbles in the flow channel, making it easier for bubbles to separate from the liquid phase.

[0050] When the gas-liquid two-phase flow from the hydrogen-alkali gas-liquid separator 4 or the oxygen-alkali gas-liquid separator 3 enters the alkali buffer tank 9 through the gas-liquid two-phase flow inlet 13, it first passes through the fluid distributor and the diffuser 12. The fluid distributor evenly distributes the gas-liquid two-phase flow across the entire cross-section of the diffuser 12, which further disperses the gas-liquid two-phase flow into fine streams, ensuring that the gas-liquid two-phase flow is evenly distributed across the cross-section of the alkali buffer tank 9. This uniform distribution increases the contact area between the gas-liquid two-phase flow and the tank interior, which is beneficial for the rapid release and escape of bubbles.

[0051] The ultrasonic device can be installed inside the alkali buffer tank 9, for example, immersed in the alkali solution, or externally, for example, attached to the outer wall of the tank. When operating, the ultrasonic device applies ultrasonic waves to the alkali solution inside the buffer tank 9, utilizing the ultrasonic cavitation effect and mechanical vibration to promote the coalescence and release of bubbles in the alkali solution. The ultrasonic device can be integrated with the alkali buffer tank 9 to form an integrated degassing unit, eliminating the need for a separate ultrasonic release device 11. The operating frequency and power of the ultrasonic device can be adjusted according to the alkali solution processing volume and degassing requirements.

[0052] Through the synergistic effect of the above structures, the alkaline solution in the alkaline solution buffer tank 9 undergoes degassing through pressure drop expansion, degassing through baffle 15 extending the path, degassing through three-dimensional porous filling skeleton 14 intercepting and coalescing, degassing through fluid distributor and diffuser 12 uniform distribution, and degassing assisted by ultrasonic device. The combined effect of multiple degassing mechanisms maximizes the reduction of gas content in the alkaline solution.

[0053] Please see the appendix Figure 1 The alkaline buffer tank 9 is a single unit. One of the outlets of the hydrogen-alkali gas-liquid separator 4 and the oxygen-alkali gas-liquid separator 3 is connected to the inlet of the alkaline buffer tank 9 via a pipeline assembly.

[0054] Specifically, in one embodiment, there is one alkali buffer tank 9. The outlet of either the hydrogen-alkali gas-liquid separator 4 or the oxygen-alkali gas-liquid separator 3 is connected to the inlet of the alkali buffer tank 9 via a piping assembly. Either the hydrogen-side or oxygen-side alkali solution enters the alkali buffer tank 9 for degassing. The degassed alkali solution is then pumped back to the hydrogen-alkali gas-liquid separator 4 and / or the oxygen-alkali gas-liquid separator 3 by the second circulation pump 10, or directly pumped back to the electrolyzer 1. This embodiment using a single alkali buffer tank 9 has the advantages of fewer devices, simpler piping, smaller footprint, and lower investment cost, making it suitable for cost-sensitive applications or those with limited installation space.

[0055] Since only one alkali solution enters the alkali buffer tank 9 in this embodiment, there is no risk of mixing between the hydrogen and oxygen side alkali solutions, therefore, there is no need to install a check valve to prevent mixing. However, the gas discharged from the vent of the alkali buffer tank 9 is either hydrogen or oxygen, so a flame arrester still needs to be installed at the vent to prevent backfire. To ensure system safety, a gas concentration monitoring sensor can also be installed at an appropriate location to monitor the hydrogen and oxygen concentrations in the pipeline in real time. When the detected concentration exceeds a preset safety threshold, the control system issues an alarm and automatically closes the liquid drain valve 2 and the second circulation pump 10, while simultaneously cutting off the system power supply.

[0056] The above safety measures work synergistically with the degassing function of the alkali buffer tank 9 to ensure safe system operation while removing bubbles.

[0057] Please see the appendix Figure 2 and attached Figure 3 There are two alkali buffer tanks, including a first buffer tank and a second buffer tank. The outlet of the hydrogen-alkali gas-liquid separator 4 is connected to the inlet of the first buffer tank through a pipeline assembly, and the outlet of the oxygen-alkali gas-liquid separator 3 is connected to the inlet of the second buffer tank through a pipeline assembly. The outlets of the first and second buffer tanks are connected to the inlet of the second circulating pump 10 via a pipeline assembly.

[0058] Specifically, the outlet of the hydrogen-alkali gas-liquid separator 4 is connected to the inlet of the first buffer tank via a piping assembly, and the outlet of the oxygen-alkali gas-liquid separator 3 is connected to the inlet of the second buffer tank via a piping assembly. Specifically, a liquid drain valve 2 is installed between the outlet of the hydrogen-alkali gas-liquid separator 4 and the inlet of the first buffer tank, and a liquid drain valve 2 is also installed between the outlet of the oxygen-alkali gas-liquid separator 3 and the inlet of the second buffer tank. The two liquid drain valves 2 are typically controlled synchronously, maintaining a consistent opening degree. The opening degree is adjusted simultaneously according to the overall liquid level on both the hydrogen and oxygen sides to maintain stable system operation.

[0059] The outlets of the first and second buffer tanks are connected to the inlet of the second circulation pump 10 via a conduit assembly. The hydrogen-side alkaline solution, after degassing in the first buffer tank, flows out from its outlet; the oxygen-side alkaline solution, after degassing in the second buffer tank, flows out from its outlet. The two degassed alkaline solutions mix at the confluence point and then enter the inlet of the second circulation pump 10, which pumps them back to the hydrogen-alkali gas-liquid separator 4 and / or the oxygen-alkali gas-liquid separator 3, or directly back to the electrolyzer 1.

[0060] The implementation using two alkali buffer tanks 9 has the following advantages: First, the hydrogen-side alkali and oxygen-side alkali remain independent during the degassing stage, each independently removing bubbles, avoiding cross-mixing of the hydrogen and oxygen-side alkali before degassing, thus avoiding safety risks caused by the mixing of hydrogen and oxygen, and also reducing the risk of cross-contamination; Second, the two buffer tanks can operate independently according to the actual operating conditions of the hydrogen and oxygen sides respectively. For example, when the gas content of the hydrogen-side alkali is high, the residence time in the hydrogen-side buffer tank can be extended, while the oxygen side maintains normal operation; Third, the two buffer tanks can serve as backups for each other. When one buffer tank needs to be inspected or maintained, the other buffer tank can continue to work, improving the continuous operation capability of the system.

[0061] To prevent potential safety hazards caused by the mixing of trace amounts of dissolved hydrogen and oxygen in the collection pipeline after degassing, this embodiment also adopts the following safety measures: A one-way valve is installed on the pipeline between the outlet of the second circulation pump 10 and the inlet of the hydrogen-alkali gas-liquid separator 4 and / or the inlet of the oxygen-alkali gas-liquid separator 3 to prevent backflow of gas and liquid from the pressurized container to the second circulation pump 10 during shutdown. Flame arresters should be installed at the vents of each alkali buffer tank 9 to prevent backfire. In addition, a gas concentration monitoring sensor is installed at an appropriate location to monitor the hydrogen and oxygen concentrations in the pipeline in real time. This gas concentration monitoring sensor is electrically connected to the control system. When the gas concentration monitoring sensor detects that the hydrogen or oxygen concentration exceeds a preset safety threshold, the control system issues an audible and visual alarm signal and automatically closes the liquid drain valve 2 and the second circulation pump 10, putting the system into a safe shutdown state.

[0062] Furthermore, the first and second buffer tanks can be configured with independent internal structures. For example, a baffle 15 and / or a three-dimensional porous filling skeleton 14 can be installed inside the first buffer tank, and a fluid distributor and a diffuser 12 can be installed inside the second buffer tank. Alternatively, different combinations of internal structures can be configured according to the different degassing requirements of the hydrogen and oxygen sides.

[0063] Please see the appendix Figure 1 and attached Figure 3 The outlet of the second circulation pump 10 is connected in sequence to the alkali cooler 6, the filter 7, the alkali flow meter 8 and the inlet of the electrolytic cell 1 through a pipeline assembly.

[0064] Specifically, the alkaline solution, after degassing in the alkaline buffer tank 9, is pumped out by the second circulation pump 10 and, instead of returning to the hydrogen-alkali gas-liquid separator 4 or the oxygen-alkali gas-liquid separator 3, is directly sent to the alkaline cooler 6 for cooling. The cooled alkaline solution is then filtered by the filter 7 and its flow rate is measured by the alkaline flow meter 8 before finally returning to the inlet of the electrolytic cell 1, completing the alkaline solution circulation. Compared to the aforementioned scheme where the outlet of the second circulation pump 10 returns to the gas-liquid separator, this implementation eliminates the secondary residence process of the degassed alkaline solution in the gas-liquid separator, allowing the "clean" degassed alkaline solution to enter the electrolytic cell 1 more quickly. This helps reduce the residence time of the alkaline solution in the circulation path, preventing the degassed alkaline solution from carrying air bubbles again in the gas-liquid separator, thereby more effectively maintaining a low alkaline solution gas content.

[0065] In this embodiment, the degassed alkali solution is directly pumped back to the electrolytic cell 1 by the second circulation pump 10. For a system equipped with a first circulation pump 5, the first circulation pump 5 and the second circulation pump 10 can work together. The first circulation pump 5 is responsible for pumping the alkali solution separated from the hydrogen-alkali gas-liquid separator 4 and the oxygen-alkali gas-liquid separator 3 back to the electrolytic cell 1, maintaining the alkali flow rate in the main circulation loop; the second circulation pump 10 is responsible for directly replenishing the degassed alkali solution to the electrolytic cell 1, further reducing the gas content of the alkali solution entering the electrolytic cell 1. The two alkali solutions can merge upstream or downstream of the alkali cooler 6 and then return to the electrolytic cell 1 together. It should be noted that when only Scheme 3 (such as...) is used... Figure 3 In the system shown, the degassed alkali solution is directly returned to the electrolytic cell 1. In this case, the first circulation pump 5 can be omitted, and the alkali solution circulation can be maintained solely by the second circulation pump 10, resulting in a simpler system structure. Those skilled in the art can choose whether or not to configure the first circulation pump 5 based on actual needs.

[0066] This implementation method is particularly suitable for application scenarios that require extremely high gas content in the alkali solution and high system response speed, such as electrolytic hydrogen production systems that require frequent start-stop or variable load operation.

[0067] Although various specific embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that the technical features of the above embodiments can be arbitrarily combined, substituted, or modified without departing from the principles and spirit of the present invention, and such combined, substituted, or modified technical solutions also fall within the protection scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A gas-liquid separation system for hydrogen production by alkaline water electrolysis, comprising an electrolytic cell (1), a hydrogen-alkali gas-liquid separator (4), an oxygen-alkali gas-liquid separator (3), a first circulating pump (5), an alkali cooler (6), a filter (7), an alkali flow meter (8), at least one alkali buffer tank (9), a second circulating pump (10), and multiple piping assemblies, characterized in that: The outlet of the electrolytic cell (1) is connected to the inlet of the hydrogen-alkali gas-liquid separator (4) and the inlet of the oxygen-alkali gas-liquid separator (3) respectively through a pipeline assembly. The outlet of the hydrogen-alkali gas-liquid separator (4) and the outlet of the oxygen-alkali gas-liquid separator (3) are respectively connected to the inlet of the first circulating pump (5) through a pipeline assembly. The outlet of the first circulating pump (5) is connected in sequence to the alkali cooler (6), the filter (7), the alkali flow meter (8) and the inlet of the electrolytic cell (1) through a pipeline assembly; The outlet of the hydrogen-alkali gas-liquid separator (4) and / or the outlet of the oxygen-alkali gas-liquid separator (3) are also connected to the inlet of the alkali buffer tank (9) through a pipeline assembly. The outlet of the alkali buffer tank (9) is connected to the inlet of the second circulation pump (10) through a pipeline assembly. The outlet of the second circulation pump (10) is connected to the inlet of the hydrogen-alkali gas-liquid separator (4) and / or the inlet of the oxygen-alkali gas-liquid separator (3) through a pipeline assembly, or to the inlet of the electrolytic cell (1). The alkaline buffer tank (9) is an atmospheric pressure vessel or a negative pressure vessel; the alkaline buffer tank (9) is provided with a baffle plate (15) and / or a three-dimensional porous filling skeleton (14); and an ultrasonic device is provided inside or outside the alkaline buffer tank (9).

2. The gas-liquid separation system for alkaline water electrolysis hydrogen production according to claim 1, characterized in that: An ultrasonic release device (11) is provided on the pipeline assembly between the outlet of the second circulating pump (10) and the inlet of the hydrogen-alkali gas-liquid separator (4) and / or the inlet of the oxygen-alkali gas-liquid separator (3).

3. The gas-liquid separation system for alkaline water electrolysis hydrogen production according to claim 1, characterized in that: The alkaline buffer tank (9) is provided with a gas-liquid two-phase flow inlet (13), and a fluid distributor and a diffuser (12) are provided at the gas-liquid two-phase flow inlet (13).

4. The gas-liquid separation system for alkaline water electrolysis hydrogen production according to claim 1, characterized in that: A liquid discharge valve (2) is provided on the pipeline assembly between the outlet of the hydrogen-alkali gas-liquid separator (4) and the alkali buffer tank (9) and / or on the pipeline assembly between the outlet of the oxygen-alkali gas-liquid separator (3) and the alkali buffer tank (9).

5. A gas-liquid separation system for alkaline water electrolysis hydrogen production according to claim 1, characterized in that: The alkaline buffer tank (9) is one, and one of the outlets of the hydrogen-alkali gas-liquid separator (4) and the oxygen-alkali gas-liquid separator (3) is connected to the inlet of the alkaline buffer tank (9) through a pipeline assembly.

6. The gas-liquid separation system for alkaline water electrolysis hydrogen production according to claim 1, characterized in that: There are two alkaline buffer tanks (9), including a first buffer tank and a second buffer tank; The outlet of the hydrogen-alkali gas-liquid separator (4) is connected to the inlet of the first buffer tank through a pipe assembly, and the outlet of the oxygen-alkali gas-liquid separator (3) is connected to the inlet of the second buffer tank through a pipe assembly; the outlets of the first buffer tank and the second buffer tank are connected to the inlet of the second circulating pump (10) after being gathered through the pipe assembly.

7. The gas-liquid separation system for alkaline water electrolysis hydrogen production according to claim 1, characterized in that: The outlet of the second circulating pump (10) is connected in sequence to the alkali cooler (6), the filter (7), the alkali flow meter (8) and the inlet of the electrolytic cell (1) through a pipeline assembly.

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