Alkaline water electrolysis hydrogen production system with waste heat utilization

Abstract

The invention discloses an alkaline water electrolysis hydrogen production system with a waste heat utilization function. The alkaline water electrolysis hydrogen production system comprises an alkaline electrolytic bath, a pure water supply device, a waste heat exchange device, a temperature control assembly and a matched connecting pipeline. The waste heat exchange device is connected to a water supplementing pipeline between the pure water tank and the alkaline electrolytic bath in series, a waste heat input connector is communicated with the waste heat output end of the alkaline electrolytic bath, a waste heat output connector is communicated with the waste heat backflow end of the alkaline electrolytic bath, and waste heat generated by operation of the electrolytic bath is recycled to preheat supplementing water. And the temperature control assembly dynamically adjusts the flow of the waste heat carrier according to a temperature signal at the water outlet end of the water supplementing pipeline, so that the supplementing water accurately reaches the temperature required by the process when entering the electrolytic bath. Efficient recycling of waste heat of the electrolytic cell is achieved, traditional additional heating equipment is replaced, system operation energy consumption is reduced by 15% or above, a main body structure of an existing electrolytic cell does not need to be greatly transformed, the transformation cost is low, applicability is high, and the method can be widely applied to industrial-grade alkaline water electrolysis hydrogen production scenes.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production technology, and more specifically to an alkaline water electrolysis system for hydrogen production with waste heat utilization. Background Technology

[0002] Alkaline water electrolysis for hydrogen production is one of the most mature and widely used hydrogen production technologies. Its core component is the alkaline electrolyzer, which decomposes water into hydrogen and oxygen by applying direct current to the electrolyte solution. During the electrolysis reaction, a large amount of heat is generated due to the internal resistance of the electrolyzer and the presence of side reactions. If this heat is not handled in time, it will cause the temperature of the electrolyzer to rise, affecting the electrolysis efficiency and equipment life. Therefore, existing technologies typically use cooling systems to cool the electrolyzer and directly discharge the waste heat into the environment, resulting in energy waste.

[0003] Meanwhile, the normal operation of an alkaline electrolyzer requires water replenishment to maintain a stable electrolyte solution concentration, and the water replenishment must reach a specific temperature range to ensure efficient electrolysis. In existing technologies, the replenishment water usually needs to be preheated by additional heating equipment (such as electric heaters, steam heaters, etc.), which not only consumes additional energy but also requires a certain preheating time, prolonging the start-up cycle of the hydrogen production system and increasing operating costs.

[0004] Therefore, how to recover and utilize the waste heat generated by alkaline electrolyzers for hydrogen production and preheat the makeup water has become a key issue in improving the economy and energy utilization rate of alkaline water electrolysis hydrogen production systems. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects in the prior art and provide an alkaline water electrolysis hydrogen production system with waste heat utilization.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: An alkaline water electrolysis hydrogen production system with waste heat utilization, comprising: An alkaline electrolytic cell is connected to an electrolyte inlet, a hydrogen outlet, an oxygen outlet, a waste heat output end, and a waste heat reflux end. A pure water supply device that stores and supplies makeup water to the electrolyzer; it is connected to the electrolyte inlet of the alkaline electrolyzer via a makeup water pipeline; The waste heat exchange device includes heat exchange pipes and a heat exchange cavity for heat exchange between each other, wherein the heat exchange pipes are connected in series on the water supply pipe. The heat exchange chamber is connected to the waste heat output end and the waste heat return end through waste heat circulation pipelines at both ends, thereby forming a waste heat utilization loop, in which the waste heat carrier circulates. Temperature control components include a water temperature sensor located at the end of the water supply pipeline near the alkaline electrolysis cell, a flow regulating valve electrically connected to the water temperature sensor, and an intelligent controller with a PLC controller as its core. The flow regulating valve is located on the waste heat circulation pipeline.

[0007] Furthermore, the waste heat carrier is the electrolyte in the alkaline electrolytic cell, and the high-temperature electrolyte flows out from the waste heat output end and flows back into the waste heat return end through the waste heat exchange device.

[0008] Furthermore, the waste heat utilization includes two independent waste heat utilization circuits arranged in parallel. The two waste heat utilization circuits are respectively connected to the cathode chamber and the anode chamber and establish their own waste heat carrier circulation, forming a hydrogen-side circuit and an oxygen-side circuit respectively. The hydrogen-side circuit and the oxygen-side circuit are connected to heat exchange chambers at different locations on the same waste heat exchange device.

[0009] Furthermore, the waste heat utilization circuit includes an outlet main pipe, outlet branch pipes, a one-way valve, a return main pipe, and a return branch pipe. Outlet branch pipes and return branch pipes are installed through the side walls of each electrode frame of the electrolytic cell, so that the waste heat carrier forms a circulation in each electrode chamber. Each outlet branch pipe is connected to the outlet main pipe, and a one-way valve is installed on the outlet branch pipe. Each return branch pipe is connected to the return main pipe. The outlet main pipe is connected to the inlet end of the heat exchange chamber, and the outlet end of the heat exchange chamber is connected to the return main pipe.

[0010] Furthermore, the outgoing branch pipe is located in the upper middle part of the electrolyte layer in the electrolytic cell, and the waste heat return branch pipe is located in the lower middle part of the electrolyte layer; a forced circulation pump is provided on the waste heat utilization circuit.

[0011] Furthermore, the alkaline solution output is dynamically matched according to the temperature distribution of the electrolysis chamber. An independent temperature sensor is set in the electrolysis chamber, and an electric control valve is installed on each output branch pipe. All temperature sensors are connected to the PLC controller via a bus connection. The PLC controller has a built-in temperature distribution mapping module that processes the received temperature sensor data and forms a temperature distribution thermogram of the electrolytic cell to identify the high-temperature electrolysis chamber. The high-temperature electrolysis chamber is set as the priority flow chamber.

[0012] Furthermore, the waste heat exchange device is a shell-and-tube heat exchanger, the heat exchange pipeline is the inner tube of the shell-and-tube heat exchanger, the heat exchange cavity is an outer tube sleeved outside the inner tube, and the shell-and-tube heat exchanger is provided with at least two independent heat exchange cavities, which are respectively connected to the hydrogen-side circuit and the oxygen-side circuit.

[0013] Furthermore, the water supply pipeline is provided with a bypass pipeline connected in parallel to the waste heat exchange device, and the bypass pipeline is provided with a bypass valve; the PLC controller is connected to the bypass valve for control.

[0014] Furthermore, the water supply pipeline is equipped with a circulation loop, the starting point of which is connected to the downstream of the waste heat exchange device, and the ending point is connected to the pure water tank. A circulation regulating valve is installed on the circulation loop, and the PLC controller is connected to the circulation regulating valve for control.

[0015] A method for utilizing waste heat from an alkaline water electrolysis hydrogen production system includes the following steps: S1, start the alkaline electrolytic cell, introduce an electrolyte solution into the electrolytic cell and apply direct current, the electrolytic cell performs the water electrolysis reaction to generate hydrogen and oxygen, and at the same time generate a high-temperature waste heat carrier; S2, start the booster pump on the water supply pipeline, and the supply water in the pure water tank enters the inner heat exchange tube of the waste heat exchange device at a flow rate of 0.8-1.2m / s; S3, the high-temperature waste heat carrier enters the heat exchange chamber of the waste heat heat exchange device through the waste heat inlet pipe, and exchanges heat with the makeup water in the inner heat exchange tube in a counter-current manner. The temperature of the makeup water rises after absorbing the waste heat. S4, the water temperature sensor collects the temperature of the makeup water at the outlet of the heat exchange tube in real time and transmits the temperature signal to the PLC controller. The controller compares the detected temperature with the set temperature range and dynamically adjusts the opening of the electric flow regulating valve to control the flow rate of the waste heat carrier, so that the makeup water temperature is stabilized at 65-75℃. S5, the preheated water to the set temperature enters the electrolyte inlet of the alkaline electrolytic cell through the water supply pipeline and participates in the electrolysis reaction; the temperature of the waste heat carrier that has completed heat exchange decreases and is returned to the alkaline electrolytic cell for recycling through the waste heat outlet pipe. S6, the hydrogen and oxygen generated by the electrolyzer are collected and stored through their respective outlets.

[0016] The advantages and beneficial effects of this invention are as follows: First, by using dual-parameter linkage monitoring of liquid level and pH value, combined with a pre-stored correspondence model, real-time online judgment of alkaline concentration is achieved, solving the problem of lag in traditional manual detection.

[0017] Secondly, the control module drives the water replenishment module to automatically replenish water, precisely controlling the amount and timing of water replenishment, and stabilizing the alkaline concentration in the optimal reaction range of 28%-32%, thereby improving the efficiency of hydrogen production through water electrolysis and reducing energy consumption.

[0018] Third, the device has a simple structure and can be directly integrated with existing water electrolysis hydrogen production systems without large-scale equipment modifications, making it widely applicable.

[0019] Fourth, the entire process requires no human intervention, reducing labor costs while avoiding the safety risks associated with manual operation, and improving the automation and intelligence level of the system operation. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of an alkaline water electrolysis hydrogen production system with waste heat utilization according to the present invention; Figure 2 This is a schematic diagram of the dual-parallel waste heat utilization loop in this invention; Figure 3 This is a schematic diagram showing the connection between the two sides of the pole frame and the waste heat utilization loop pipeline in this invention; Figure 4 This is a schematic diagram of the process structure of Embodiment 4 of the present invention; Figure 5 This is a schematic diagram of the process structure of Embodiment 5 of the present invention; In the diagram: 1. Alkaline electrolytic cell; 2. Electrolyte inlet; 3. Hydrogen outlet; 4. Oxygen outlet; 5. Waste heat output end; 6. Waste heat return end; 7. Water supply line; 8. Waste heat exchanger; 9. Heat exchange line; 10. Heat exchange chamber; 11. Waste heat utilization circuit; 12. Water temperature sensor; 13. Flow regulating valve; 14. Cathode chamber; 15. Anode chamber; 16. Hydrogen side circuit; 17. Oxygen side circuit; 18. Main outlet pipe; 19. Branch outlet pipe; 20. Check valve; 21. Return main pipe; 22. Return branch pipe; 23. Electrode frame sidewall; 24. Electrically controlled valve; 25. Temperature sensor; 26. Bypass line; 27. Bypass valve; 28. Circulation circuit; 29. ​​Second flow regulating valve; 30. Pure water tank; 31. Water supply branch; 32. First flow regulating valve; 33. Flow detector. Detailed Implementation

[0021] 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.

[0022] This technical solution focuses on the core requirements of waste heat recovery and utilization and safe and stable operation of the system in the alkaline water electrolysis hydrogen production process. Based on the traditional hydrogen production system, it optimizes the structural design and enhances intelligent control to achieve efficient waste heat recovery, precise and balanced control of electrolyzer temperature, and safe isolation of hydrogen and oxygen.

[0023] Example 1: The present invention discloses an alkaline water electrolysis hydrogen production system with waste heat utilization, comprising an alkaline electrolysis cell 1, a pure water supply device, a waste heat exchange device 8, and a temperature control component, which are the basic carriers for realizing waste heat utilization and hydrogen production functions. The alkaline electrolyzer 1, serving as the core of the hydrogen production reaction, is equipped with an electrolyte inlet 2, a hydrogen outlet 3, an oxygen outlet 4, a waste heat output end 5, and a waste heat return end 6. This satisfies the core requirements for generating hydrogen and oxygen through water electrolysis and provides a channel for the extraction and return of the waste heat carrier. A pure water supply device delivers deionized water with a resistivity ≥18 MΩ·cm to the electrolyzer via a water supply pipeline 7, ensuring the purity requirements of the electrolysis reaction. A booster pump is installed on the water supply pipeline 7 to stably control the water flow rate at 0.8-1.2 m / s, ensuring high efficiency in the heat exchange process of the waste heat exchange device 8. The waste heat exchange device 8 adopts a "heat exchange pipeline 9 + heat exchange chamber 10" structural design, i.e., a shell-and-tube heat exchanger structure. The heat exchange pipeline 9 is connected in series with the water supply pipeline 7, and the heat exchange chamber 10 is connected to the waste heat output end 5 and the return end of the electrolyzer via a waste heat circulation pipeline, forming a closed waste heat utilization loop 11. Figure 1 As shown, the high-temperature waste heat carrier generated by the electrolyzer can circulate within the loop and exchange heat with the cold water in the water supply pipeline 7, fundamentally solving the energy waste problem caused by the direct discharge of waste heat from the electrolyzer in traditional hydrogen production systems; the temperature control component, with a PLC controller as its core, combined with the water temperature sensor 12 and the flow regulating valve 13, achieves precise control of the heat exchange process, avoids the water supply temperature from deviating from the process requirement range, and ensures the efficient and stable operation of the electrolysis reaction.

[0024] The alkaline electrolytic cell 1 is a skid-mounted alkaline electrolytic cell 1 with a rated working pressure of 0.6-1.0 MPa and a rated working temperature consistent with the temperature of the waste heat carrier. The pure water supply device includes a pure water tank 30 and a water supply pump, which are used to store and supply makeup water to the electrolyzer. The outlet of the pure water tank 30 is connected to the electrolyte inlet 2 of the alkaline electrolyzer 1 through a water supply pipeline 7. A booster pump is also installed on the water supply pipeline 7. The booster pump is located between the pure water tank 30 and the waste heat exchange device 8 and is used to increase the flow rate of the makeup water in the heat exchange tube. The booster pump is a horizontal centrifugal pump.

[0025] A waste heat exchange device 8 is installed on the water supply pipeline 7. The waste heat exchange device 8 includes a heat exchange chamber 10 and a heat exchange pipeline 9 installed within the heat exchange chamber 10. The supply water flows within the heat exchange pipeline 9. The waste heat inlet pipe is connected to the waste heat output end 5 of the alkaline electrolytic cell 1, and the waste heat outlet pipe is connected to the waste heat return end 6 of the alkaline electrolytic cell 1. The waste heat carrier generated by the electrolytic cell, i.e., the high-temperature electrolyte in the alkaline electrolytic cell 1, flows within the heat exchange chamber 10, preheating the supply water through heat exchange. The heat exchange pipeline 9 is the inner tube of a shell-and-tube heat exchanger, and the supply water flows within the inner tube, with the waste heat carrier and supply water flowing in a counter-current heat exchange direction.

[0026] Temperature control components include a water temperature sensor 12 located at one end of the water supply pipeline 7 near the alkaline electrolysis tank 1, a flow regulating valve 13 electrically connected to the water temperature sensor 12, and an intelligent controller. The water temperature sensor 12 is located at the outlet end of the heat exchange pipeline 9 and is used to monitor the temperature of the preheated water supply in real time. The flow regulating valve 13 is located on the waste heat circulation pipeline and is used to adjust the flow rate of the waste heat carrier according to the water temperature in the water supply pipeline 7, so that the temperature of the supply water is stabilized within the process requirement range. The intelligent controller is used to adjust the opening of the electric flow regulating valve 13 according to the detection signal of the temperature sensor 25, thereby controlling the flow rate of the waste heat carrier.

[0027] Example 2: In Example 1, the waste heat carrier is the electrolyte in the alkaline electrolytic cell 1. The high-temperature electrolyte flows out from the waste heat output end 5 and returns to the waste heat return end 6 through the waste heat exchange device 8. It does not differentiate between different types of electrolyte within the electrolytic cell. Specifically, the electrolytic chambers within the electrolytic cell refer to electrolytic units separated by diaphragms, including a cathode chamber 14 and an anode chamber 15. The chamber closest to the cathode is the cathode chamber 14, where the introduced alkaline electrolyte undergoes a reduction reaction to produce hydrogen gas. The chamber closest to the anode is the anode chamber 15, where the electrolyte undergoes an oxidation reaction to produce oxygen gas. The diaphragm allows ions in the electrolyte to pass through to form a conductive circuit, while simultaneously preventing hydrogen and oxygen from mixing, ensuring gas purity and operational safety. If the waste heat carriers drawn from the cathode chamber 14 and the anode chamber 15 are not distinguished, since some hydrogen or oxygen will dissolve in the alkaline solution, the alkaline solutions in the cathode chamber 14 and the anode chamber 15 will be mixed and drawn out, which will increase the mixed content of hydrogen in oxygen and oxygen in the alkaline solution. With the circulation, the amount of mixture will increase cumulatively, and the subsequent gas-liquid separator will be unable to separate them, resulting in impure products and increased danger.

[0028] This embodiment addresses the drawback of the aforementioned embodiments where direct mixing of hydrogen-side and oxygen-side electrolytes could lead to the mixing of dissolved hydrogen and oxygen gases. Specifically, this embodiment designs a dual-path, parallel, independent waste heat utilization circuit 11. The two circuits correspond to the cathode chamber 14 (hydrogen production side) and anode chamber 15 (oxygen production side) of the electrolyzer, respectively, each establishing a waste heat carrier circulation, forming a hydrogen-side circuit 16 and an oxygen-side circuit 17. Both circuits are connected to different independent heat exchange chambers 10 on the same waste heat exchange device 8. This design is based on the principle of "hydrogen-oxygen isolation," utilizing the physical separation between the cathode chamber 14 and anode chamber 15 inside the electrolyzer to allow the electrolytes on both sides to flow and exchange heat independently within their respective circuits. This eliminates the contact between dissolved hydrogen on the hydrogen side and dissolved oxygen on the oxygen side from the source, completely avoiding the risk of explosion. Meanwhile, the parallel design of the dual-circuit system did not reduce the waste heat recovery efficiency. On the contrary, by increasing the heat exchange contact area, the makeup water can fully absorb the waste heat of the electrolyte on both sides, further improving the energy utilization rate. This design not only meets the safety specifications but also aligns with the core objective of maximizing waste heat recovery.

[0029] Specifically, to achieve orderly circulation and precise diversion of the waste heat carrier in each electrolysis chamber, this embodiment optimizes the specific structure of the waste heat utilization circuit 11, and sets up a main outlet pipe 18, an outlet branch pipe 19, a one-way valve 20, a return main pipe 21, a return branch pipe 22, and a forced circulation pump. For example... Figure 2 As shown in the figure, two independent waste heat utilization loops 11 are set up in parallel, namely the hydrogen side loop 16 and the oxygen side loop 17 in the figure. The structure of the two loops is basically the same. The difference is that the two waste heat utilization loops 11 are respectively connected to the cathode chamber 14 and the anode chamber 15 and establish their own waste heat carriers, thus forming the hydrogen side loop 16 and the oxygen side loop 17. The hydrogen-side circuit 16 and oxygen-side circuit 17 are connected to heat exchange chambers 10 at different locations on the same waste heat exchange device 8. In actual use, the two circuits heat the makeup water together, thereby simplifying the structural design and effectively utilizing the waste heat. Taking one circuit as an example, the waste heat utilization circuit 11 includes a main outlet pipe 18, branch outlet pipes 19, a one-way valve 20, a main return pipe 21, and a branch return pipe 22. The branch outlet pipes 19 and 22 are installed through the side walls 23 of each electrode frame of the electrolytic cell, so that the waste heat carrier forms a circulation in each electrode chamber. Each branch outlet pipe 19 is connected to the main outlet pipe 18, and a one-way valve 20 is installed on the branch outlet pipe 19. Each branch return pipe 22 is connected to the main return pipe 21. The main outlet pipe 18 is connected to the inlet end of the heat exchange chamber 10, and the outlet end of the heat exchange chamber 10 is connected to the main return pipe 21. The end of the main return pipe 21 branches into the corresponding branch return pipes 22 for each electrode chamber (not shown in the figure).

[0030] The lead-out branch pipe 19 and the return branch pipe 22 pass through the side walls 23 of each electrode frame of the electrolytic cell, such as... Figure 3 As shown, the electrolyte layers are located in the upper and lower middle sections, respectively. The principle behind this arrangement is that the electrolyte temperature is higher in the upper middle section, allowing for the extraction of more high-temperature carriers as the waste heat output end 5. The lower middle section, acting as a reflux end, ensures that the cooled electrolyte is evenly distributed throughout the entire chamber, guaranteeing uniform heat exchange and cooling. The one-way valve 20 effectively prevents electrolyte backflow and cross-flow between different chambers, further enhancing the hydrogen-oxygen isolation effect. Considering the insufficient natural circulation power of directly drawing electrolyte from the electrolytic cell chamber, a variable frequency forced circulation pump is added. This design ensures the flow rate of the waste heat carrier within the loop through external force, guaranteeing heat exchange efficiency. Simultaneously, the variable frequency function dynamically adjusts the flow rate according to subsequent temperature control requirements, providing power support for precise temperature control.

[0031] Example 3: To address the issue of uneven temperature distribution in the stacked electrolysis chambers of the electrolyzer, a dynamic flow control mechanism based on temperature distribution was designed, which is the core optimization point for achieving stable electrolyzer operation. The design principle involves installing an independent temperature sensor 25 in each electrolysis chamber, such as... Figure 3 As shown, the temperature sensors 25 can be arranged in an externally attached distribution, where an array of thermocouples or distributed fiber optic grating (FBG) sensors are attached to the outer wall of the electrode frame or the outer side of the sealing surface of the electrolysis chamber, arranged along the axial direction of the electrolytic stack, with each measuring point corresponding to the outer wall temperature of a chamber. Alternatively, the temperature sensing element can be pre-embedded in the electrode frame. Mounting holes are pre-drilled in the non-flow channel area of ​​the metal electrode frame (nickel-based alloy or nickel-plated carbon steel) of the electrolysis chamber, and miniature thermocouples or thin-film resistance thermometers are pre-embedded within them. The measuring end is close to the inner wall of the electrode frame, and the wire is led out through the sealed wiring hole on the side of the electrode frame and connected to the signal acquisition module. Furthermore, the number of temperature sensors 25 can be designed according to specific needs; temperature sensors 25 can be installed in each chamber or spaced apart (reducing the number of sensors and lowering costs).

[0032] Temperature data is aggregated to the PLC controller via a bus connection. The controller's built-in temperature distribution mapping module processes the data to generate a longitudinal temperature distribution heat map of the electrolyzer, accurately identifying high-temperature electrolysis chambers. These high-temperature chambers are designated as priority flow chambers and given priority flow control. Simultaneously, each branch pipe 19 is equipped with an electrically controlled valve 24. Based on the temperature information fed back from the heat map, the PLC controller dynamically adjusts the opening of the electrically controlled valve 24 according to the logic of "more flow control for high-temperature chambers, less for low-temperature chambers": the higher the temperature of the chamber, the larger the opening of the electrically controlled valve 24, resulting in a larger waste heat carrier circulation and a stronger cooling effect; the lower the temperature of the chamber, the smaller the opening of the electrically controlled valve 24 is, maintaining basic circulation. The advantage of this design is that it overcomes the problem of localized overheating or overcooling caused by traditional "average flow control," enabling targeted and enhanced cooling of high-temperature areas. This keeps the internal temperature of the electrolyzer balanced within the optimal reaction range, not only improving the efficiency of hydrogen production through electrolysis but also preventing damage to core components such as electrodes and diaphragms from localized high temperatures, thus extending the equipment's service life. Its original design purpose was to solve the problem of uneven temperature caused by differences in internal resistance distribution and reaction intensity in stacked electrolytic cells, and to further optimize the stability of system operation.

[0033] Correspondingly, regarding the structural design of the waste heat exchange device 8, this embodiment also adopts a shell-and-tube heat exchanger, with the heat exchange pipe 9 as the inner tube and the heat exchange cavity 10 as the outer tube sleeved outside the inner tube. At least two independent heat exchange cavities 10 are provided, corresponding to the hydrogen-side and oxygen-side circuits 17 respectively. Figure 2As shown in the diagram. The design principle utilizes the compact structure and high heat exchange efficiency of the shell-and-tube heat exchanger. A heat exchange channel is formed through the gap between the inner and outer tubes, allowing the waste heat carrier and the makeup water to flow in a counter-current heat exchange direction (the waste heat carrier flows in the heat exchange chamber 10, and the makeup water flows in the inner tube). This counter-current heat exchange maximizes the temperature difference, improves heat exchange efficiency, and ensures that the makeup water fully absorbs the waste heat. The tubes are made of 316L stainless steel, suitable for the corrosive environment of alkaline electrolytes. This material meets the corrosion resistance and strength requirements for industrial use.

[0034] Example 4: To address the extreme situation of excessively high preheating temperature of the makeup water, the solution provides two optimization options, including the design of the circulation loop 28 and the bypass pipeline 26.

[0035] Regarding the design of bypass pipe 26, specifically, as follows: Figure 4 As shown, the water supply pipeline 7 is provided with a bypass pipeline 26 connected in parallel to the waste heat exchange device 8, and the bypass pipeline 26 is provided with a bypass valve 27; the controller is connected to the bypass valve 27 for control, and when the preheating water temperature is too high, the PLC controller automatically and fully opens the bypass valve 27 so that the water inlet bypasses the heat exchange device, preventing high temperature from damaging the sealing structure of the electrolytic cell or causing cavitation.

[0036] Example 5: In the above embodiment four, the control principle is: to adjust the temperature detected by the outlet water temperature sensor 12 by changing the amount of water supplied to the heat exchanger and bypass pipeline 26. It can only reduce the overall temperature of the electrolyzer by increasing the proportion of low-temperature water. First, it cannot accurately cool the high-temperature area of ​​the electrolyzer. Second, the excess heat in the waste heat utilization circuit 11 cannot be removed by the heat exchanger, which may cause the temperature of the waste heat carrier to exceed the target range.

[0037] The improvement of this embodiment compared to embodiment four is that, as follows: Figure 5 As shown, this embodiment includes a circulation loop 28. The starting point of the circulation loop 28 is connected downstream of the waste heat exchange device 8, and the ending point is connected to the pure water tank 30. A first flow regulating valve 32 and a flow detector 33 are installed on the water replenishment branch 31 that enters the electrolyte inlet 2. A second flow regulating valve 29 is installed on the circulation loop 28. The PLC controller is connected to the flow detector 33, the first flow regulating valve 32, and the second flow regulating valve 29. The flow detector 33 detects the flow rate entering the electrolyte inlet 2, and the opening degree of the first flow regulating valve 32 and the second flow regulating valve 29 is controlled by the flow rate.

[0038] The principle of the circulation loop 28 design is to set up a circulation loop 28 in the water supply pipe 7, connecting the downstream of the waste heat exchange device 8 to the pure water tank 30. Through the coordination of the circulation loop 28 and the opening of the flow regulating valve 13 set on the upper part of the water supply branch 31, under the control of the PLC controller, while maintaining the water supply to meet the electrolysis requirements, excess heat is carried back to the pure water tank 30 for storage via the circulating water flow. This embodiment combines the structure of Embodiment 3, and its advantages are: on the one hand, it can fully absorb the excess heat of the waste heat carrier, ensuring that the temperature of the waste heat carrier drops to the target range, avoiding the backflow of high-temperature carrier from affecting the electrolytic cell; on the other hand, combined with the dynamic flow control mechanism, the cooled waste heat carrier can be accurately delivered to the high-temperature chamber, achieving targeted cooling and further ensuring the temperature balance inside the electrolytic cell. The initial intention of this design is to overcome the limitations of the traditional bypass pipe 26 design, achieve maximum utilization of waste heat and precise temperature control, and improve the stability and flexibility of system operation.

[0039] The operation flow of the alkaline water electrolysis hydrogen production system with waste heat utilization described in this embodiment is as follows: 1. System Start-up: First, inject 30% KOH electrolyte into alkaline electrolytic cell 1. After the liquid level reaches 80% of the electrolytic cell volume, start the electrolytic cell power supply and apply DC power. The electrolytic cell will start the water electrolysis reaction. Hydrogen and oxygen are produced during the reaction. At the same time, the electrolyte temperature rises to 85℃ due to the heat generated by internal resistance.

[0040] 2. Water supply and preheating: Start the booster pump on the water supply line 7. Deionized water (initial temperature 25℃) in the pure water tank 30 enters the inner heat exchange line 9 of the shell-and-tube heat exchanger at a flow rate of 1.0m / s. At the same time, the high-temperature KOH electrolyte (85℃) in the electrolytic cell enters the heat exchange chamber 10 through the waste heat inlet pipe, forming a countercurrent heat exchange with the supply water in the inner tube. The heat of the high-temperature electrolyte is transferred to the supply water through the inner tube wall.

[0041] 3. Precise Temperature Control: The water temperature sensor 12 collects the temperature of the makeup water at the outlet of the heat exchange tube in real time and transmits the signal to the PLC controller. When the detected water temperature is below 68℃, the controller controls the electric flow regulating valve 13 to increase the opening, thereby increasing the flow rate of the high-temperature electrolyte and improving the heat exchange efficiency. When the detected water temperature is above 72℃, the controller controls the electric flow regulating valve 13 to decrease the opening, thereby reducing the flow rate of the high-temperature electrolyte and preventing the makeup water temperature from becoming too high. Through dynamic adjustment, the makeup water temperature is stably maintained at 70±2℃.

[0042] 4. Water replenishment and waste heat return: The preheated water to 70°C enters the electrolyte inlet 2 of the alkaline electrolytic cell 1 through the water replenishment pipe 7 and directly participates in the electrolysis reaction without additional preheating; the temperature of the KOH electrolyte after heat exchange drops to 75°C and returns to the electrolytic cell through the waste heat outlet pipe to continue participating in the electrolysis reaction and heat generation cycle.

[0043] 5. Product collection: The hydrogen and oxygen generated by the electrolyzer enter the drying and purification device through their respective outlets. After dehydration and impurity removal, they are stored in the gas storage tank. The purity of hydrogen can reach 99.99% and the purity of oxygen can reach 99.2%.

[0044] The system performance test data for this embodiment is as follows: Energy consumption comparison: Traditional electric heating preheating method consumes 1.2 kWh / Nm³ of electricity. 3 H2, this system requires no additional heating, reducing overall energy consumption by 16.7%; Startup time comparison: The traditional system takes 60 minutes to reach stable hydrogen production from startup, while this system only takes 42 minutes, reducing the startup time by 30%; Temperature stability: After 72 hours of continuous operation, the temperature fluctuation range of the makeup water is ≤±1℃, and the temperature fluctuation range of the electrolytic cell is ≤±2℃, significantly improving the stability of the operating conditions.

[0045] In summary, this system achieves efficient recovery and utilization of waste heat from alkaline electrolytic cell 1 by integrating waste heat exchange device 8 into water supply pipeline 7. It has multiple advantages such as energy saving, efficiency improvement and stable operating conditions, and has high industrial promotion value.

[0046] 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 alkaline water electrolysis hydrogen production system with waste heat utilization, characterized in that, include: An alkaline electrolytic cell is connected to an electrolyte inlet, a hydrogen outlet, an oxygen outlet, a waste heat output end, and a waste heat reflux end. A pure water supply system that stores and supplies makeup water to the electrolyzer; It is connected to the electrolyte inlet of the alkaline electrolytic cell via a water supply pipeline; The waste heat exchange device includes heat exchange pipes and a heat exchange cavity for heat exchange between each other, wherein the heat exchange pipes are connected in series on the water supply pipe. The heat exchange chamber is connected to the waste heat output end and the waste heat return end through waste heat circulation pipelines at both ends, thereby forming a waste heat utilization loop, in which the waste heat carrier circulates. Temperature control components include a water temperature sensor located at the end of the water supply pipeline near the alkaline electrolysis cell, a flow regulating valve electrically connected to the water temperature sensor, and an intelligent controller with a PLC controller as its core. The flow regulating valve is located on the waste heat circulation pipeline.

2. The alkaline water electrolysis hydrogen production system with waste heat utilization according to claim 1, characterized in that, The waste heat carrier is the electrolyte in the alkaline electrolytic cell. The high-temperature electrolyte flows out from the waste heat output end and flows back into the waste heat return end through the waste heat exchange device.

3. The alkaline water electrolysis hydrogen production system with waste heat utilization according to claim 1, characterized in that, The waste heat utilization includes two sets of independent waste heat utilization circuits set in parallel. The two sets of waste heat utilization circuits are respectively connected to the cathode chamber and the anode chamber and establish their own waste heat carrier circulation, forming a hydrogen-side circuit and an oxygen-side circuit respectively. The hydrogen-side circuit and the oxygen-side circuit are connected to heat exchange chambers at different locations on the same waste heat exchange device.

4. A water electrolysis hydrogen production system with waste heat utilization according to any one of claims 1-3, characterized in that, The waste heat utilization circuit includes an outlet main pipe, outlet branch pipes, a one-way valve, a return main pipe, and a return branch pipe. Outlet branch pipes and return branch pipes are installed through the side walls of each electrode frame of the electrolytic cell, so that the waste heat carrier forms a circulation in each electrode chamber. Each outlet branch pipe is connected to the outlet main pipe and a one-way valve is installed on the outlet branch pipe. Each return branch pipe is connected to the return main pipe. The outlet main pipe is connected to the inlet end of the heat exchange chamber, and the outlet end of the heat exchange chamber is connected to the return main pipe.

5. The alkaline water electrolysis hydrogen production system with waste heat utilization according to claim 4, characterized in that, The outgoing branch pipe is located in the upper middle part of the electrolyte layer in the electrolytic cell, and the waste heat return branch pipe is located in the lower middle part of the electrolyte layer; a forced circulation pump is provided on the waste heat utilization circuit.

6. The alkaline water electrolysis hydrogen production system with waste heat utilization according to claim 4, characterized in that, The amount of alkali solution drawn out is dynamically matched according to the temperature distribution of the electrolysis chamber. An independent temperature sensor is set in the electrolysis chamber, and an electric control valve is installed on each branch pipe. The temperature sensors are connected to the PLC controller through a bus connection. The PLC controller has a built-in temperature distribution mapping module that processes the received temperature sensor data and forms a temperature distribution thermogram of the electrolytic cell to identify the high-temperature electrolysis chamber. The high-temperature electrolysis chamber is set as the priority flow chamber.

7. The alkaline water electrolysis hydrogen production system with waste heat utilization according to claim 3, characterized in that, The waste heat exchange device is a shell-and-tube heat exchanger, the heat exchange pipeline is the inner tube of the shell-and-tube heat exchanger, the heat exchange cavity is an outer tube sleeved outside the inner tube, and the shell-and-tube heat exchanger is provided with at least two independent heat exchange cavities, which are respectively connected to the hydrogen side circuit and the oxygen side circuit.

8. The alkaline water electrolysis hydrogen production system with waste heat utilization according to claim 1, characterized in that, The water supply pipeline is provided with a bypass pipeline connected in parallel to the waste heat exchange device, and the bypass pipeline is provided with a bypass valve; the PLC controller is connected to the bypass valve for control.

9. The alkaline water electrolysis hydrogen production system with waste heat utilization according to claim 1, characterized in that, The water supply pipeline is equipped with a circulation loop. The starting point of the circulation loop is connected to the downstream of the waste heat exchange device, and the ending point is connected to the pure water tank. A first flow regulating valve and a flow detector are installed on the water supply branch entering the electrolyte inlet. A second flow regulating valve is installed on the circulation loop. The PLC controller is connected to the flow detector, the first flow regulating valve, and the second flow regulating valve. The flow detector detects the flow rate entering the electrolyte inlet, and the opening degree of the first flow regulating valve and the second flow regulating valve is controlled by the flow rate.

10. A method for utilizing waste heat from an alkaline water electrolysis hydrogen production system, employing the alkaline water electrolysis hydrogen production system as described in claim 1, characterized in that... Includes the following steps: S1, start the alkaline electrolytic cell, introduce an electrolyte solution into the electrolytic cell and apply direct current, the electrolytic cell performs the water electrolysis reaction to generate hydrogen and oxygen, and at the same time generate a high-temperature waste heat carrier; S2, start the booster pump on the water supply pipeline, and the supply water in the pure water tank enters the inner heat exchange tube of the waste heat exchange device at a flow rate of 0.8-1.2m / s; S3, the high-temperature waste heat carrier enters the heat exchange chamber of the waste heat heat exchange device through the waste heat inlet pipe, and exchanges heat with the makeup water in the inner heat exchange tube in a counter-current manner. The temperature of the makeup water rises after absorbing the waste heat. S4, the water temperature sensor collects the temperature of the makeup water at the outlet of the heat exchange tube in real time and transmits the temperature signal to the PLC controller. The controller compares the detected temperature with the set temperature range and dynamically adjusts the opening of the electric flow regulating valve to control the flow rate of the waste heat carrier, so that the makeup water temperature is stabilized at 65-75℃. S5, preheated to the set temperature, the makeup water enters the electrolyte inlet of the alkaline electrolytic cell through the makeup water pipeline and participates in the electrolysis reaction; The temperature of the waste heat carrier that has completed heat exchange decreases, and it is returned to the alkaline electrolytic cell for recycling through the waste heat outlet pipe; S6, the hydrogen and oxygen generated by the electrolyzer are collected and stored through their respective outlets.

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