Electrolytic cell circulating system with double recovery of thermal and pressure energy

Abstract

The application discloses a kind of with heat energy and pressure energy double recovery's electrolytic cell circulating system, system includes electrolytic cell, circulating pump, main pipeline, shunt branch;Circulating pump outlet is divided into main pipeline and shunt branch, shunt branch is sequentially provided with heat exchanger and jet pump along flow direction;Circulating pump is operated according to rated load condition, part of electrolyte enters electrolytic cell through main pipeline, and excess electrolyte enters shunt branch, releases heat through heat exchanger to preheat supplement and realizes heat energy recovery, after cooling, enter ejector, as power fluid drive jet pump, pump the backflow liquid in gas-liquid separator bottom, and realize pressure energy recovery, after mixing, enter gas-liquid separator and carry out gas-liquid separation, complete circulation.The application prolongs the life of circulating pump by full load operation, and realizes heat energy and pressure energy double efficient recovery, simultaneously avoids vibration, cavitation and life attenuation problem caused by low load operation, suitable for wide load, high energy efficiency operation of electrolytic hydrogen production device.

Description

Technical Field

[0001] This invention relates to the field of alkaline water electrolysis hydrogen production technology, specifically to an electrolyzer circulation system with dual recovery of thermal and pressure energy. Background Technology

[0002] In the alkaline water electrolysis hydrogen production process, the electrolyte circulation system is the core unit ensuring the stable and efficient operation of the electrolysis reaction. As the power core of the system, the operating conditions of the electrolyte circulation pump directly determine the system's reliability, service life, and energy consumption. Engineering practice and application data show that the electrolyte circulation pump operates at its optimal hydraulic state, with minimal vibration, low temperature rise, and longest service life under rated full-load conditions. However, under low-load, low-flow, variable-frequency speed reduction, or throttling conditions, the pump is prone to problems such as local backflow, eddy currents, cavitation, and seal failure, significantly shortening its service life and greatly increasing the failure rate.

[0003] In practical hydrogen production systems, electrolyzers typically need to operate under varying conditions within a wide load range, requiring electrolyte flow rates far lower than the rated flow rate of the circulating pump. Traditional regulation methods, such as frequency conversion regulation, outlet throttling, or direct bypass recirculation, all cause the circulating pump to deviate from its optimal full-load operating conditions for extended periods, exacerbating pump damage. Furthermore, the electrolyte at the circulating pump outlet carries a significant amount of high-temperature heat and high-pressure energy; direct throttling or simple recirculation results in severe energy waste and reduces the overall system energy efficiency.

[0004] While existing technologies employ individual solutions such as waste heat recovery, bypass reflux, or jet-assisted circulation, none systematically address the core engineering contradiction of "long lifespan of the circulating pump under full load and short lifespan under low load," nor do they achieve integrated solutions encompassing "pump lifespan extension under constant full load + heat energy recovery + pressure energy recovery + wide load adjustment of the electrolyzer." Therefore, developing an electrolyte circulation system that ensures both continuous full-load, long-life operation of the circulating pump and efficient recovery of excess flow energy, along with precise adjustment of the electrolyzer load, has become a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects in the prior art and provide an electrolytic cell circulation system with dual recovery of thermal energy and pressure energy.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] An electrolytic cell circulation system with dual recovery of thermal and pressure energy includes an electrolytic cell and a circulation pump. The outlet of the circulation pump is provided with a main pipeline and a branch pipeline in parallel. The circulation pump operates according to a preset load. Its main pipeline is connected to the electrolytic cell. The flow rate of the electrolyte in the main pipeline is adapted to the wide load adjustment operation of the electrolytic cell. The remaining electrolyte is distributed to the branch pipeline.

[0008] The main pipeline connects the outlet of the circulating pump to the inlet of the electrolytic cell.

[0009] A branch circuit is used to recover and utilize the energy of the electrolyte in a cascade manner. A heat exchanger and a jet pump are sequentially arranged along the electrolyte flow direction on the branch circuit. The branch circuit is connected to the heat source side of the heat exchanger, the cold source side inlet of the heat exchanger is connected to the end of the cold material to be replenished, and the cold source side outlet is connected to the replenishment demand end of the main circulation loop. The jet pump includes a power inlet, a suction port, and a mixing outlet. The power inlet is connected to the heat source side outlet, the suction port is connected to the low-pressure return end of the main circulation loop, and the mixing outlet is connected to the low-pressure circulation replenishment end of the main circulation loop, forming a forced internal circulation of the liquid phase in the low-pressure zone of the main circulation loop.

[0010] Instead of installing a heat exchanger for cooling the electrolyte in the main circulation loop, the electrolyte in the main circulation loop is cooled through a branch circuit, allowing for rapid reheating and use of the electrolytic cell after low-load standby cooling.

[0011] Furthermore, the main circulation loop is equipped with a separator for gas-liquid separation. The separator includes one or more combinations of hydrogen separator, oxygen separator, and alkali separator. The gas outlet of the separator is used to discharge hydrogen or oxygen generated during the electrolysis process, and the liquid outlet is connected to the inlet of the circulation pump through the return pipe of the main pipeline.

[0012] Furthermore, a main regulating valve is provided on the main pipeline, and a diversion regulating valve is provided on the diversion branch. By controlling the two regulating valves, the flow ratio of the diversion branch is changed so that the circulating pump can maintain the preset load operation.

[0013] Furthermore, the cold material end includes any one or more of the system raw material liquid, alkaline solution, or pure water; the liquid replenishment demand end includes the electrolytic cell water replenishment port and the separator liquid replenishment port.

[0014] Furthermore, the low-pressure reflux end includes a reflux pipe and a guide pipe leading out from the low dead zone of the liquid phase side of each separator.

[0015] Furthermore, the low-pressure circulation replenishment end includes a return pipe on the inlet side of the circulation pump, an alkali tank, and a low-pressure collection section of the separator.

[0016] Furthermore, an aftercooler is also provided on the branch line, and the aftercooler is located downstream of the injection pump.

[0017] Furthermore, it also includes a control unit. The controller of the control unit is electrically connected to the main regulating valve, the branch regulating valve, and the circulating pump. The controller calculates the target flow rate Q1 required to enter the electrolytic cell according to the load command of the electrolytic cell, and controls the opening of the main regulating valve to match Q1. At the same time, the controller controls the circulating pump to operate under a preset load condition, outputting a constant total flow rate Q_total, and controls the opening of the branch regulating valve so that the flow rate Q2 of the branch is Q_total - Q1. When the load of the electrolytic cell changes to correspond to the change of Q1 from 0 to 100%, the total flow rate Q_total at the outlet of the circulating pump always remains at the preset flow rate.

[0018] Furthermore, the circulating pump is a centrifugal pump, a magnetic pump, or a canned motor pump, and its operating condition is the full load point of rated speed, rated flow rate, and rated power;

[0019] The heat exchanger is a plate heat exchanger, a shell-and-tube heat exchanger, or a coaxial heat exchanger.

[0020] The advantages and beneficial effects of this invention are as follows:

[0021] This invention achieves a perfect balance between the industry-wide contradiction of constant full-load operation of the circulating pump and wide-load adjustment of the electrolyzer through a dual-loop architecture of the main circulation loop and branch circuits. Furthermore, it realizes cascaded energy recovery and global optimization of the system flow field. Compared to traditional technologies, its core breakthrough lies in the first-ever integrated solution of pump life extension under constant full-load conditions, heat recovery, pressure energy recovery, and wide-load adjustment of the electrolyzer, solving a long-standing technical challenge in this field. The innovative design of the main circulation loop without heat exchange equipment enables rapid heating of the electrolyzer for the first time, perfectly adapting to the characteristics of fluctuating green electricity supply and providing a foundation for the coupled development of alkaline water electrolysis hydrogen production and green electricity. Core technologies support this system. The multi-point directional suction design of the jet pump and separator dead zones achieves, for the first time, forced circulation within the separator without sludge buildup, fundamentally solving the liquid phase sludge problem in large-volume separators. Simultaneously, the coordinated design of energy cascade recovery and system operating condition control allows the branch circuit to not only perform energy recovery but also serve as an auxiliary control circuit for system operating conditions, achieving the design goal of a single branch circuit with multiple functions. Ultimately, this system achieves the operational goals of a wide-load, long-life, high-efficiency, and highly stable alkaline water electrolysis hydrogen production system, suitable for various alkaline water electrolysis hydrogen production devices, especially suitable for hydrogen production projects coupled with green electricity, and possesses extremely high engineering application value. Attached Figure Description

[0022] Figure 1 This is one of the process diagrams of the electrolytic cell circulation system for dual recovery of thermal and pressure energy according to the present invention;

[0023] Figure 2 This is the second schematic diagram of the electrolytic cell circulation system for dual recovery of thermal and pressure energy according to the present invention;

[0024] In the diagram: 1. Electrolyzer; 2. Circulation pump; 3. Main pipeline; 4. Branch pipeline; 5. Main circulation loop; 6. Cold source side inlet; 7. Cold source side outlet; 8. Power inlet; 9. Suction port; 10. Mixing outlet; 11. Heat source side outlet; 12. Heat exchanger; 13. Jet pump; 16. Hydrogen separator; 17. Oxygen separator; 18. Return pipe; 19. Main pipeline regulating valve; 20. Branch pipeline regulating valve; 22. Alkali tank; 24. Electrolyzer water inlet; 25. Separator liquid inlet; 26. Guide pipe; 27. Aftercooler. Detailed Implementation

[0025] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0026] This invention relates to an electrolytic cell circulation system with dual recovery of thermal and pressure energy. The core of this system is a constant load operation design for the circulation pump 2, which addresses the industry pain point of pump damage under low load operation in traditional systems. (It can be understood that this constant load can be full load or any set load that allows the circulation pump 2 to operate within an optimal operating range.) This system abandons the single-loop design of the traditional electrolytic cell 1 circulation system and adopts a dual-loop parallel architecture of main circulation loop 5 + branch loop 4. The main loop is responsible for supplying the core electrolyte for the electrolysis reaction, while the branch loop 4 is responsible for energy recovery of excess electrolyte and auxiliary system regulation. The process design revolves around the core objectives of "energy recovery, pump life extension, and wide load adaptability".

[0027] This system breaks away from the traditional single-loop design mode of the electrolytic cell 1 circulation system and constructs a dual-loop architecture with the main circulation loop 5 and the branch circuit 4 running in parallel. The main circulation loop 5 is responsible for the transportation and circulation of the core electrolyte of the electrolysis reaction, while the branch circuit 4 is responsible for absorbing the excess output flow of the circulation pump 2 and completing energy recovery and auxiliary regulation of system operating conditions.

[0028] First, the main circulation loop 5 is the main loop for the electrolyte, such as... Figure 1 , 2 As shown, the specific process is as follows: Circulation pump 2 → main pipeline 3 → electrolyzer 1 → separator (including hydrogen separator, oxygen separator, and alkali separator) → return pipe 18 → circulation pump 2, which is a closed-loop circulation circuit. No heat exchange equipment may be installed on the main circulation circuit 5. The circuit only completes the transport of electrolyte, electrolysis reaction, and gas-liquid separation, which is the core process channel for electrolytic hydrogen production.

[0029] Second, there is a branch line 4. The outlet of the circulating pump 2 is connected in parallel with the main pipeline 3 and the branch line 4. Through the pipeline architecture of the main pipeline 3 and the branch line 4 connected in parallel and the process logic of energy cascade recovery, the main pipeline 3 is part of the main circulation loop 5, and the branch line 4 is the part connected in parallel with it. The branch line 4 is led out in parallel from the outlet of the circulating pump 2 and is installed in sequence along the electrolyte flow direction with a flow regulating valve 20, a heat exchanger 12 (heat source side), and a jet pump 13 (power inlet 8). Optionally, according to the system cooling requirements, a post-cooler 27 can be added downstream of the jet pump 13 as the core branch of the system's energy cascade recovery. At the same time, through the liquid replenishment port of the heat exchanger 12, the suction port 9 of the jet pump 13, and the mixing outlet 10, energy transfer and fluid coordination with the main circulation loop 5 are achieved.

[0030] Thirdly, the cold material supply and liquid replenishment pipelines are connected to the cold source side of heat exchanger 12 and the pure water tank and dilute alkali tank to provide low-temperature raw materials for heat exchange. The liquid replenishment pipeline transports the cold material preheated by heat exchanger 12 to the water replenishment port 24 of the electrolytic cell and the liquid replenishment port 25 of the separator to complete the precise liquid replenishment of the system and recover and utilize the excess heat of the main circulation loop 5 to cool down the alkali solution in the system.

[0031] Fourthly, there are low-pressure reflux and low-pressure circulation replenishment pipelines. The low-pressure reflux end is connected to the suction port 9 of the jet pump 13. The low-pressure reflux end includes the liquid phase dead zone of the separator and the reflux pipe 18 to realize the suction of fluid in the low-pressure zone. The low-pressure circulation replenishment pipeline transports the fluid mixed by the jet pump 13 to the inlet of the circulation pump, the alkali tank 22, and the low-pressure liquid collection section of the separator to complete the reflux of the fluid after pressure energy recovery.

[0032] This system achieves integrated technical goals including wide load regulation of electrolytic cell 1, efficient dual recovery of thermal and pressure energy, and optimization of the entire system flow field, while perfectly adapting to industry application needs with fluctuating green electricity supply. The following section provides a detailed explanation of the system's core pipeline structure and process design principles.

[0033] Branch circuit 4 performs energy cascade recovery and utilization of the diverted electrolyte. A heat exchanger 12 and a jet pump 13 are sequentially arranged along the electrolyte flow direction on branch circuit 4. Branch circuit 4 is connected to the heat source side of heat exchanger 12. The cold source side inlet 6 of heat exchanger 12 is connected to the end of the cold material to be replenished, and the cold source side outlet 7 is connected to the replenishment demand end of the main circulation loop 5. The replenishment demand end can provide targeted fresh raw material replenishment to the replenishment ends at various locations on the main circulation loop 5 that require replenishment, and... The heat exchanger 12 (heat recovery heat exchanger 12) preheats the makeup liquid, which also absorbs excess heat in the system to cool the system. The cold material end includes any one or more of the system raw material liquid, alkali solution or pure water. The makeup liquid demand end includes the electrolytic cell water inlet 24 and the separator liquid inlet 25. If the cooling capacity is insufficient, a heat exchanger 12 can be added on the branch line 4 and the material can be cooled by cooling water. The added heat exchanger 12 can be set at the outlet of the jet pump 13.

[0034] The jet pump 13 includes a power inlet 8, a suction port 9, and a mixing outlet 10. The power inlet 8 is connected to the heat source side outlet 11, and the suction port 9 is connected to the low-pressure return end of the main circulation loop 5. The mixing outlet 10 is connected to the low-pressure circulation replenishment end of the main circulation loop 5. This forms a cascade utilization of energy through waste heat recovery and pressure recovery. The low-pressure return end can be a dead zone in multiple low-pressure areas of the system. Especially in systems with large production volumes, there are many problems caused by poor circulation in many places. The suction port can lead out branch pipes from each poor circulation area for targeted forced flow circulation.

[0035] The low-pressure reflux end (connected to the suction port 9) includes a reflux pipe 18 and a guide pipe 26 leading out from the low-level dead zone prone to accumulation on the liquid phase side of each separator. The core function of the jet pump 13 is designed to address the dead zone positions where electrolyte easily accumulates and forms dead zones within the separator, enabling forced internal circulation without dead zones. The core connection part is the liquid collection end / accumulation chamber at the bottom of the separator's liquid phase zone, which can be precisely summarized into three key parts, as follows:

[0036] 1. The lowest point of the separator's bottom is the collection tank / accumulation pool; this is the core low-level area where the liquid phase of the separator settles naturally, and it is also the core dead corner where the electrolyte is most prone to sludge accumulation and the flow rate approaches zero. The suction port 9 is connected here, and multiple points can be set to directly suction the static accumulation at the bottom, achieving forced flow from the source of sludge accumulation. (The original return pipe 18, which was drawn from a fixed position, could not cover a large area of ​​electrolyte circulation, especially for larger volume separators.)

[0037] 2. The end of the liquid phase guide channel on the inner wall of the separator; the inner wall of the separator is usually provided with a liquid phase guide channel to guide the electrolyte to converge. The end of the channel is prone to forming a fluid backflow dead zone. The suction port 9 is connected to this, and the fluid in the guide channel can be driven to flow through negative pressure suction to avoid liquid accumulation in the channel.

[0038] 3. The liquid boundary region below the gas-liquid interface of the separator; this region is at the critical position of gas-liquid separation, where the fluid flow rate is slow and local stagnation dead zones are easily formed. The suction port 9 is connected to this region, and the fluid in this region can be disturbed by negative pressure, which can not only avoid liquid accumulation in the boundary region, but also assist gas-liquid separation and prevent the liquid phase from carrying gas and affecting the circulation.

[0039] The core commonality of the above-mentioned connection parts is that they are all located in the low-position, low-flow-rate, and easily liquid-accumulating structural dead zones on the liquid side of the separator. The suction port 9 is connected here, and through the continuous negative pressure suction of the jet pump 13, the originally static / low-speed liquid phase in the separator can form a directional and continuous forced flow, completely eliminating dead zones and sludge accumulation. While ensuring gas-liquid separation efficiency, it also makes the system liquid phase circulation smoother and avoids problems such as uneven local concentration and temperature caused by sludge accumulation. It is understandable that control valves can be set at the outlets of each low-pressure return to allow for proportioning or periodic switching to optimize the configuration.

[0040] The low-pressure circulation replenishment end includes the return pipe 18 on the inlet side of the circulation pump, the alkali tank 22, and the low-pressure collection section of the separator; the low-pressure circulation replenishment end is the destination for the high-pressure mixture from the mixing outlet 10 of the jet pump 13 after pressure energy recovery; the low-pressure circulation replenishment end is the low-pressure side replenishment position of the entire system's closed-loop circulation, as detailed below:

[0041] 1. Return pipe 18 on the inlet side of the circulating pump: The mixture pressurized by the jet pump 13 is fed into this pipe, which directly increases the feed pressure and flow rate at the inlet of the circulating pump, improves the NPSH at the pump inlet, and allows the recovered pressure energy to be directly converted into the liquid supply power of the circulating pump 2, maximizing the reuse of pressure energy and ensuring that the circulating pump 2 supplies liquid stably to the main pipeline 3 at full load.

[0042] 2. The system's alkali tank serves as the low-pressure storage and homogenization point for the system's electrolyte, acting as a basic replenishment point. The mixture is replenished here by the jet pump 13, achieving homogenization of the low-pressure electrolyte, supplementing the circulating volume of the alkali tank, and simultaneously allowing the high-temperature, high-pressure mixture to undergo secondary pressure and temperature buffering within the storage tank. This prevents local parameter fluctuations caused by direct replenishment to the pump inlet, ensuring stable storage and circulation of the electrolyte on the low-pressure side of the system.

[0043] 3. The low-pressure liquid collection section of the separator is the downstream low-pressure liquid phase collection end of the separator, belonging to the fine replenishment end. Including the matching liquid collection structures of the hydrogen separator 16, oxygen separator 17, and alkali separator, the low-pressure liquid collection section is the initial collection area for the separator's return liquid. The mixed liquid is replenished here by the jet pump 13, which can directly drive the flow of the low-pressure liquid phase in this area, enhance the liquid phase venting effect of the gas-liquid treatment unit, further avoid localized dead zones, and allow the separator's forced internal circulation to synergize with the overall low-pressure circulation of the system.

[0044] I. Operating Principle of Circulating Pump 2 under Constant Full Load

[0045] It also includes a control unit, whose controller is electrically connected to the main regulating valve 19, the diversion regulating valve 20, and the circulating pump 2 (it can be understood that flow meters, pressure sensors, and other devices can also be attached to the main pipeline 3 and the diversion branch 4 for monitoring). The controller calculates the target flow rate Q1 required to enter the electrolytic cell 1 according to the load command of the electrolytic cell 1, and controls the opening of the main regulating valve 19 to match Q1. At the same time, the controller controls the circulating pump 2 to operate under a preset load condition, outputting a constant total flow rate Q_total, and controls the opening of the diversion regulating valve 20 so that the flow rate Q2 of the diversion branch 4 is Q_total - Q1. When the load of the electrolytic cell 1 changes to correspond to the change of Q1 from 0 to 100%, the total flow rate Q_total at the outlet of the circulating pump 2 always remains at the preset flow rate. By linking the control unit to adjust the main regulating valve 19 and the diversion regulating valve 20, the circulating pump 2 is kept at full load with rated speed, rated flow, and rated power, outputting a constant total flow rate Q_total. The electrolyte flow rate Q1 required by the electrolytic cell 1 is precisely adjusted by the main regulating valve 19. Excess electrolyte flow rate Q2 = Q_total - Q1 automatically enters the diversion branch 4, completely avoiding problems such as cavitation, vibration, and seal failure caused by low-load operation of the circulating pump 2, thus extending the pump body life from the root.

[0046] II. Principle of Energy Cascade Recovery

[0047] Branch circuit 4 adopts a tiered utilization logic of first recovering heat energy and then recovering pressure energy. The high-temperature and high-pressure electrolyte output by circulating pump 2 first enters the heat source side of heat exchanger 12 and exchanges heat with the low-temperature material on the cold source side, transferring heat to the cold material to complete waste heat recovery. At the same time, the electrolyte is cooled down. The cooled high-pressure electrolyte serves as the driving fluid of jet pump 13. It is ejected at high speed through the nozzle to form a negative pressure, which draws the low-pressure return liquid in the system. During the mixing and diffusion process, the pressure energy that would have been lost due to throttling is converted into the conveying power of the return liquid, thus completing the efficient recovery and reuse of pressure energy.

[0048] III. Temperature control principle of main circulation loop 5 without heat exchange

[0049] Traditional systems require the addition of a heat exchanger 12 to the main circulation loop 5 to cool down the heat generated by the electrolysis reaction. However, this solution can transfer all cooling functions to the branch loop 4, achieving overall system temperature control through heat exchange of the distributed electrolyte. This allows the main circulation loop 5 to retain only the functions of heat generation and heat storage, avoiding interference from the heat exchange equipment on the flow field of the main loop and laying the foundation for rapid heating and constant temperature operation of the electrolytic cell 1.

[0050] Specifically, this system addresses typical special operating conditions in alkaline water electrolysis hydrogen production, such as sudden load changes in electrolyzer 1 caused by fluctuations in green electricity supply, localized siltation caused by long-term operation of the separator, cavitation risk caused by low inlet pressure of the circulating pump, and insufficient system cooling capacity caused by excessive heat generation from high load in electrolyzer 1. Relying on the existing pipeline structure and valve configuration, the system achieves rapid and accurate adaptation to various special operating conditions through pipeline on / off control, valve opening adjustment, and dynamic adjustment of fluid flow ratio. All adaptation strategies do not require the addition of new core equipment and are characterized by fast response speed and strong engineering operability. In the case of a sudden change from zero load or low load to high load in the electrolyzer, this condition is mainly matched for application scenarios where the green electricity supply suddenly increases. At this time, the temperature of the electrolyzer 1 is low due to the low load operation, while the optimal operating temperature of the electrolysis reaction is 70~90℃. It is necessary to quickly heat up to the optimal temperature to ensure hydrogen production efficiency. In traditional systems, because the main circulation loop 5 is equipped with a heat exchanger 12, it will continue to dissipate heat even when operating at low load, and cannot achieve rapid heating. However, this solution relies on the design advantage of the main circulation loop 5 without heat exchange equipment, and forms an adaptation strategy of full flow circulation in the main loop and minimum flow blocking in the branch 4, which perfectly solves this problem. For example, when the control unit receives a high-load operation command from electrolyzer 1, it will fully open the main regulating valve 19 in a very short time, while simultaneously adjusting the branch regulating valve 20 to its minimum opening of less than 5%, ensuring only micro-flow of fluid in the pipeline to prevent pressure buildup. This allows almost all of the rated total flow output from the circulating pump 2 to enter the main pipeline 3, maximizing the electrolyte circulation volume in the main circulation loop 5. At this time, the flow direction of the branch pipeline 4 will also be precisely controlled, and the feed regulating valves of the pure water tank and dilute alkali tank on the cold source side of the heat exchanger 12 will be closed, cutting off... For cold material replenishment, heat exchanger 12 only completes micro-heat exchange through the residual fluid in the pipeline, with almost no cooling effect, to avoid the low temperature effect of the branch 4 affecting the main circuit in reverse. The jet pump 13 only maintains low power operation because the flow rate of the branch 4 is extremely small. The suction port 9 only slightly draws the electrolyte from the main return pipe 18 and no longer draws from the dead corner of the separator. The mixing outlet 10 only replenishes a small amount of mixed liquid into the alkali tank and does not replenish the low temperature fluid to the inlet of the circulating pump, ensuring that the electrolyte delivered by the circulating pump 2 to the main circuit is always in a high temperature state. Since the main circulation loop 5 has no heat exchange equipment, the high-temperature electrolyte at full flow rate circulates rapidly in a closed loop between the circulation pump 2, electrolytic cell 1, and separator. The electrolysis reaction continuously generates heat as the load increases, and the heat carried by the electrolyte continuously accumulates in the main loop without any heat dissipation loss. This allows the temperature of electrolytic cell 1 to rise rapidly from room temperature or low temperature to the optimal operating temperature of 70~90℃ in a short period of time, achieving a rapid response to sudden increases in green electricity supply. When the temperature of electrolytic cell 1 reaches the optimal operating temperature, the entire system has a large load fluctuation range and the ability to adapt to different operating conditions. During this fluctuation process, the circulation pump 2 always operates at the optimal flow load to avoid damage caused by pump blockage.

[0051] IV. Forced circulation principle in low-pressure areas

[0052] By precisely connecting the suction port 9 of the jet pump 13 to the bottom liquid collection tank, the end of the guide channel, and the gas-liquid interface boundary area on the liquid side of the separator, the continuous negative pressure generated by the jet pump 13 forms a forced internal circulation inside the separator and an overall circulation in the low-pressure area of ​​the system, completely eliminating the dead zone of liquid phase accumulation and ensuring the gas-liquid separation efficiency of the separator and the uniformity of the flow field of the entire system.

[0053] In the case of localized siltation in the separator, especially in large-volume separators, the bottom liquid collection tank, the end of the guide channel, and the gas-liquid interface boundary area on the liquid side are prone to electrolyte siltation due to slow fluid flow and stagnation. This leads to uneven local electrolyte concentration and temperature, reducing gas-liquid separation efficiency and even causing pipeline blockage. This solution relies on the design of connecting the suction port 9 of the jet pump 13 to multiple dead zones of the separator through the guide pipe 26 to form an adaptive strategy of multi-point directional suction, flow ratio and periodic switching control. When siltation is detected in a certain part of the separator, the opening of the regulating valve of the guide pipe 26 for that part can be directly increased to increase the suction flow of the jet pump 13 to that part, while the suction flow of other parts is reduced. The accumulated static electrolyte is quickly extracted by negative pressure, causing the surrounding fluid to form a directional flow and eliminating siltation at the source. If siltation occurs in multiple parts of the separator at the same time, the opening of the regulating valve of the corresponding guide pipe 26 can be adjusted according to the degree of siltation in each part, and a reasonable suction flow ratio can be set to achieve simultaneous siltation in multiple parts and ensure a uniform flow field in the separator. During normal system operation, the control unit can also preset a periodic switching suction program to adjust the suction flow ratio of each guide pipe 26 at regular intervals, so that the fluid in each dead corner of the separator is always in a slight flow state, fundamentally preventing siltation. After the pumped-up sludge electrolyte is mixed with the power fluid of the jet pump 13, it will be preferentially added to the low-pressure collection section of the separator, driving the overall circulation of the liquid phase in the separator, forming a closed-loop sludge removal process of suction-recirculation-recycle (the sludge removal is to deal with the problem of uneven local concentration and temperature caused by the dead zone formed by the local sludge accumulation of electrolyte).

[0054] In cavitation prevention conditions where the inlet pressure of the circulating pump is low, the cavitation risk of the circulating pump 2 is directly related to the inlet pressure. When the inlet pressure is low, the electrolyte is prone to vaporization, forming bubbles that impact the pump body impeller, leading to impeller wear, pump body vibration, and even interruption of liquid supply. In this system, the circulating pump 2 operates at full load, which requires higher stability of the inlet pressure. Therefore, relying on the pressure energy recovery function of the jet pump 13, an adaptation strategy is formed to prioritize the injection of the mixed liquid into the inlet of the circulating pump and quickly increase the inlet static pressure. The mixing outlet 10 of the jet pump 13 originally feeds fluid into the system through three routes: the return pipe 18 on the inlet side of the circulating pump, the alkali tank, and the low-pressure collection section of the separator. When the pressure at the inlet of the circulating pump is detected to be too low, the feed ratio on the inlet side of the circulating pump will be quickly increased to over 90%, while the feed ratio to the alkali tank and the low-pressure collection section of the separator will be closed or reduced. This allows all or most of the high-pressure mixture after being pressurized by the jet pump 13 to be fed into the inlet of the circulating pump. The pressure of the mixture in the jet pump 13 is much higher than the normal or low pressure at the inlet of the circulating pump. After the high-pressure mixture is fed in, it will directly increase the static pressure at the inlet of the circulating pump, quickly improve the net positive suction head (NPSH) at the pump inlet, and increase it to more than 1.5 times the original state, thus completely eliminating the risk of cavitation. If the inlet pressure remains low, the flow rate of the branch line 4 can be appropriately increased to enhance the power fluid pressure of the jet pump 13, thereby increasing the pressurization effect of the mixture and further increasing the inlet pressure of the circulating pump. At the same time, the fluid status of the main return pipe 18 should be checked to ensure that no gas is entrained into the inlet of the circulating pump, thus ensuring the safe operation of the circulating pump 2 from multiple dimensions.

[0055] As an improvement, in cases of insufficient system cooling capacity, which often occurs during the high-load operation of electrolytic cell 1, the increased heat generation from the electrolytic reaction and the inability of the waste heat recovery from heat exchanger 12 to meet the overall cooling requirements of the system, if the system temperature continues to rise, it will lead to a decline in electrolyte performance and aging of equipment seals. This solution utilizes the design of adding a post-cooler 27 to the branch circuit 4, forming an adaptive strategy of opening the post-cooler 27 for secondary cooling of the electrolyte. Specifically, the inlet and outlet valves of the cooling water of the post-cooler 27 downstream of the jet pump 13 are opened, allowing the jet pump 13 to mix the electrolyte. The electrolyte enters the aftercooler 27 for secondary heat exchange with the cooling water, and then is sent to the main circulation loop 5 (preferably, it can first be sent to the low-pressure circulation inlet of the separator, and through homogenization, the low-temperature electrolyte is slowly integrated into the main circulation loop 5 to achieve gentle cooling of the system and avoid the sudden temperature change caused by directly adding the low-temperature electrolyte to the circulation pump inlet); at the same time, the cooling water flow rate of the aftercooler 27 can be adjusted according to the actual temperature of the system to achieve precise control of the cooling effect and ensure that the temperature of the main circulation loop 5 is stable within the optimal process range of 70~90℃.

[0056] Through dual innovations in pipeline structure and process design, this system not only fundamentally solves three core industry problems in traditional electrolyzer 1 circulation systems—pump damage under low load, severe energy waste, and difficulty in adjusting wide load ranges in electrolyzer 1—but also achieves several unique technical effects that are difficult to achieve with conventional technologies in this field. These technical effects are highly synergistic and mutually supportive, achieving a performance upgrade of the alkaline water electrolysis hydrogen production circulation system from multiple dimensions, including energy efficiency, operational stability, load adaptability, equipment lifespan, and engineering applications.

[0057] Firstly, it achieves a rapid load response to adapt to fluctuations in green electricity supply, enabling wide load adjustment of electrolyzer 1 from 0% to 100% without dead zones. Relying on the dual design of the main circulation loop 5 without heat exchange equipment and the circulation pump 2 operating at constant full load, the system's response speed to load switching in electrolyzer 1 is significantly improved. When switching from low to high load, the main loop achieves rapid heating through full-flow circulation, reaching the optimal operating temperature in 5-10 minutes. The response speed is more than 60% faster than traditional systems, perfectly adapting to the sudden fluctuations in green electricity supply. When switching from high to low load, excess flow can automatically enter the branch 4 for energy recovery, without requiring any adjustment to the operating conditions of the circulation pump 2. The inlet flow rate of electrolyzer 1 can be continuously and steplessly adjusted. Within the full load range of 0-100%, the flow field pressure fluctuation deviation is ≤±2%, with no throttling or pressure buildup, ensuring stable electrolysis.

[0058] Secondly, it achieves efficient recovery of both thermal and pressure energy, significantly reducing the overall energy consumption of the system. The energy cascade recovery design of the diversion branch 4 maximizes the utilization of high-temperature thermal energy and high-pressure pressure energy in the electrolyte, with no ineffective energy loss. In terms of thermal energy recovery, the heat exchanger 12 preheats the system feed (pure water / alkaline solution), directly replacing the heating equipment of the traditional system, reducing the system heating energy consumption by more than 40%. At the same time, it effectively removes excess heat from the system, eliminating the need to add cooling equipment to the main circulation loop 5. In terms of pressure energy recovery, the jet pump 13 converts the high-pressure potential energy of the diversion electrolyte into the conveying power of the low-pressure return liquid, replacing the booster pump of the traditional system, reducing the energy consumption of the system auxiliary equipment by more than 30%, while effectively reducing throttling losses, reducing the overall operating energy consumption of the system by 25% to 30%, and significantly reducing the hydrogen production power consumption.

[0059] Thirdly, it achieves an ultra-long service life of the pump body, completely avoiding equipment damage caused by low-load operation. The circulating pump 2 maintains a predetermined stable flow load throughout the entire process, always in the optimal working state with optimal hydraulics, minimal vibration, and lowest temperature rise. It completely avoids problems such as cavitation, eddy currents, and seal failure caused by frequency conversion regulation and outlet throttling in traditional systems. This extends the service life of the circulating pump 2 by 3 to 5 times compared to traditional systems and reduces the equipment failure rate by more than 80%. At the same time, the pressurization and feeding of the pump inlet by the jet pump 13 further improves the cavitation margin at the pump inlet, avoiding pump body damage from a secondary protection perspective, and greatly improving the operational stability of the circulating pump 2.

[0060] Fourth, it achieves a non-stagnant forced circulation effect in the separator, keeping the gas-liquid separation efficiency stable at over 99.9%. Through the precise connection of the jet pump 13 suction port 9 to multiple liquid dead zones in the separator, combined with flow ratio and periodic switching control, it achieves a non-stagnant forced internal circulation of the liquid phase within the separator. This completely eliminates the stagnant dead zones in the bottom collection tank, the end of the guide tank, and the gas-liquid interface boundary area, avoiding the problem of uneven local electrolyte concentration and temperature, and ensuring stable electrolyte performance. At the same time, the forced circulation keeps the fluid in the separator in a constant state of flow, significantly improving the gas-liquid separation efficiency and keeping it stable at over 99.9%. The electrolyte droplet content in hydrogen and oxygen is reduced to below 5 ppm, effectively reducing the operating load of the subsequent gas purification system.

[0061] Fifth, it achieves an ultra-stable flow field in the main loop, without any interference from heat exchange equipment or flow field fluctuations. The pure delivery pipeline design of the main circulation loop 5 without heat exchange equipment significantly reduces the flow resistance of the electrolyte in the main loop, resulting in a uniform flow field distribution without local turbulence or pressure surges. This greatly improves the stability of the inlet pressure and flow rate of the electrolytic cell 1. At the same time, this design allows the electrolyte heat retention rate to be close to 100%, which not only enables rapid heating of the electrolytic cell 1 but also effectively ensures the constant operating temperature of the electrolytic cell 1, thereby increasing the electrolysis reaction efficiency by more than 10%.

[0062] Sixth, it achieves high adaptability in engineering, taking into account both new device design and energy-saving and life-extending retrofit of old systems. This system adopts a parallel split design, which can be completed by adding a split branch 4, heat exchanger 12 and jet pump 13 to the original circulation system. There is no need to modify the main structure of electrolyzer 1 and circulation pump 2. For new device design, the pipeline structure and process logic can be directly integrated without additional optimization of the main circulation loop 5. For existing hydrogen production systems, low-cost energy-saving and life-extending retrofit can be achieved. The retrofit cost is only 5% to 8% of the total system investment, while the energy efficiency of the system can be improved by more than 25% and the pump life can be extended by more than 3 times. It has extremely high engineering applicability and market promotion value.

[0063] Seventh, it achieves a homogeneous electrolyte circulation effect, greatly improving the overall operational stability of the system. Through the negative pressure suction and mixing replenishment of the jet pump 13, the stagnant electrolyte in the separator, the stored electrolyte in the alkali tank, and the electrolyte supplied by the circulation pump 2 are fully mixed, effectively avoiding the problem of local concentration deviation of the electrolyte and ensuring the stability of the electrolysis reaction. At the same time, the feed after preheating by the heat exchanger 12 is directly sent to the water inlet 24 of the electrolytic cell and the liquid inlet 25 of the separator, which can quickly mix with the electrolyte in the main circuit. There is no phenomenon of low-temperature cold material directly impacting the system, which greatly improves the temperature and concentration uniformity of the entire system and ensures the stable operation of the system from the fluid state level.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrolytic cell circulation system with dual recovery of thermal and pressure energy, characterized in that, It includes an electrolytic cell and a circulating pump. The outlet of the circulating pump is provided with a main pipeline and a branch pipeline in parallel. The circulating pump operates according to a preset load. Its main pipeline is connected to the electrolytic cell. The flow rate of the electrolyte in the main pipeline is adapted to the wide load adjustment operation of the electrolytic cell. The remaining electrolyte is distributed to the branch pipeline. The main pipeline connects the outlet of the circulating pump to the inlet of the electrolytic cell. A branch circuit is used to perform energy cascade recovery and utilization of the diverted electrolyte. A heat exchanger and a jet pump are sequentially arranged along the electrolyte flow direction on the branch circuit. The branch circuit is connected to the heat source side of the heat exchanger, the cold source side inlet of the heat exchanger is connected to the end of the cold material to be replenished, and the cold source side outlet is connected to the replenishment demand end of the main circulation loop. The jet pump includes a power inlet, a suction port, and a mixing outlet. The power inlet is connected to the heat source side outlet, the suction port is connected to the low-pressure return end of the main circulation loop, and the mixing outlet is connected to the low-pressure circulation replenishment end of the main circulation loop. This forms a cascade utilization of energy through waste heat recovery and pressure recovery. The main pipeline is equipped with a main regulating valve, and the branch pipeline is equipped with a branch regulating valve. By controlling the two regulating valves, the flow ratio of the branch pipeline is changed so that the circulating pump can maintain the preset load operation. It also includes a control unit. The controller of the control unit is electrically connected to the main regulating valve, the branch regulating valve and the circulating pump. The controller calculates the target flow rate Q1 required to enter the electrolytic cell according to the load command of the electrolytic cell, and controls the opening of the main regulating valve to match Q1. At the same time, the controller controls the circulating pump to operate under a preset load condition, outputting a constant total flow rate Q_total, and controls the opening of the branch regulating valve so that the flow rate Q2 of the branch is Q_total - Q1. When the load of the electrolytic cell changes to correspond to the change of Q1 from 0 to 100%, the total flow rate Q_total at the outlet of the circulating pump always remains at the preset flow rate.

2. The electrolytic cell circulation system with dual recovery of heat energy and pressure energy according to claim 1, characterized in that, The main circulation loop is equipped with a separator for gas-liquid separation. The separator includes one or more combinations of hydrogen separator, oxygen separator, and alkali separator. The gas outlet of the separator is used to discharge hydrogen or oxygen generated during electrolysis, and the liquid outlet is connected to the inlet of the circulation pump through the return pipe of the main pipeline.

3. The electrolytic cell circulation system with dual recovery of heat energy and pressure energy according to claim 1, characterized in that, The cold material end includes any one or more of the system raw material liquid, alkaline solution, or pure water; the liquid replenishment demand end includes the electrolytic cell water replenishment port and the separator liquid replenishment port.

4. The electrolytic cell circulation system with dual recovery of heat energy and pressure energy according to claim 2, characterized in that, The low-pressure reflux end includes a guide pipe leading out from the low dead zone and easy-to-accumulate area on the liquid phase side of each separator.

5. The electrolytic cell circulation system with dual recovery of heat energy and pressure energy according to claim 1, characterized in that, The low-pressure circulation replenishment end includes the return pipe on the inlet side of the circulation pump, the alkali tank, and the low-pressure collection section of the separator.

6. The electrolytic cell circulation system with dual recovery of heat energy and pressure energy according to claim 1, characterized in that, An aftercooler is also provided on the branch line, and the aftercooler is located downstream of the injection pump.

7. The electrolytic cell circulation system with dual recovery of heat energy and pressure energy according to claim 1, characterized in that, The circulating pump is a centrifugal pump, magnetic pump, or canned pump, and its operating condition is the full load point of rated speed, rated flow, and rated power. The heat exchanger is a plate heat exchanger, a shell-and-tube heat exchanger, or a coaxial heat exchanger.

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