Thermally / mass self-balancing fuel cell and method of operation thereof

Abstract

The application discloses a thermal / quality self-balanced fuel cell and a working method thereof, and solves the technical problem of low equipment integration and large volume of the existing fuel cell device, wherein the thermal / quality self-balanced fuel cell comprises a fuel cell stack, a thermal / quality self-balanced composite hydrogen storage device and a control device, the thermal / quality self-balanced composite hydrogen storage device comprises a reactor, an upper jacket, a lower jacket, a pressure gauge, a water distribution device and a spiral pipe, the reactor comprises relatively independent upper and lower reaction chambers, a rare earth hydrogen storage alloy bed layer is arranged in the upper reaction chamber, a hydrogen outlet at the top of the upper reaction chamber is connected with an anode inlet of the fuel cell stack through a pipeline, and a hydrolytic solid-state hydrogen storage material bed layer is arranged in the lower reaction chamber, and the integrated structure design breaks the circulation barrier of heat and matter between the fuel cell stack and the dual-mode hydrogen source, significantly reduces the complexity of the system, and greatly reduces the equipment volume and weight.

Description

Technical Field

[0001] This invention relates to hydrogen fuel cells, and more specifically to a heat / mass self-balancing fuel cell and its operating method. Background Technology

[0002] As a highly efficient and clean power generation device, the commercial application of fuel cells places higher demands on the reliability, energy density, and thermal management of hydrogen supply systems. Currently, hydrogen supply methods for fuel cells (especially proton exchange membrane fuel cells) are mainly divided into two categories: physical hydrogen storage (high-pressure gaseous hydrogen, cryogenic liquid hydrogen) and chemical hydrogen storage. Among them, solid-state hydrogen storage methods based on chemical hydrides have attracted widespread attention due to their high hydrogen storage density and good safety.

[0003] In solid-state hydrogen storage methods based on chemical hydrides, the hydrogen release mechanisms of solid-state hydrogen storage materials mainly include two modes: pyrolysis and hydrolysis. For example, rare-earth-based hydrogen storage alloys produce hydrogen by absorbing heat and decomposing. This mode produces hydrogen with high purity and good controllability, but the hydrogen production is an endothermic process that requires continuous external heating. Materials such as sodium borohydride and magnesium hydride can also produce hydrogen by reacting with water. This mode produces hydrogen at a fast rate, but usually requires an additional water source, and the reaction is exothermic, which would result in energy waste if not utilized.

[0004] In existing technologies, most solutions to the thermal management problem of fuel cell systems attempt to recover waste heat from the fuel cell stack. For example, Chinese utility model patent CN223579677U discloses a solid-state hydrogen storage system, and Chinese utility model patent CN223579677U discloses a solid-state hydrogen supply system and hydrogen power equipment; both of these utilize a heat exchange medium between the fuel cell stack and the hydrogen source to reuse the heat. Alternatively, Chinese utility model patent CN214505553U discloses an integrated hydrogen fuel cell power system and an electric bicycle, which uses direct introduction of cathode exhaust gas into the hydrogen source reactor wall for heat exchange. These technical solutions only achieve energy transfer in one direction, resulting in low energy utilization efficiency.

[0005] Furthermore, Chinese invention patent CN119725638A discloses a composite hydrogen storage device and a fuel cell. The composite hydrogen storage device includes a first reaction chamber and a second reaction chamber, with the first reaction chamber located within the second reaction chamber. The first reaction chamber is used to produce hydrogen through a hydrolysis reaction, while the second reaction chamber is used to produce or store hydrogen through an endothermic reaction. The first and second reaction chambers are respectively connected to a fuel cell to provide a hydrogen source for the fuel cell. While this technical solution can reuse the heat released from the hydrolysis reaction in the first reaction chamber, improving energy utilization efficiency and increasing the system's hydrogen storage density, its fuel cell still requires external energy / mass input during startup or operation to maintain stable operation of the composite hydrogen storage device. Additionally, the device has low integration and a large size. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of existing fuel cells still requiring external energy / mass input during startup or operation to maintain the stable operation of the composite hydrogen storage device, and the low integration and large size of the equipment. The invention provides a heat / mass self-balancing fuel cell and its operating method.

[0007] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0008] A heat / mass self-balancing fuel cell, characterized in that it includes a fuel cell stack, a heat / mass self-balancing composite hydrogen storage device, and a control device.

[0009] The heat / mass self-balancing composite hydrogen storage device includes a reactor, an upper jacket, a lower jacket, a pressure gauge, a water distribution device, and a spiral tube.

[0010] The reactor includes a relatively independent upper reaction chamber and a lower reaction chamber. The upper reaction chamber is equipped with a rare earth-based hydrogen storage alloy bed. A hydrogen mixing cavity is formed between the top of the rare earth-based hydrogen storage alloy bed and the inner wall of the top of the upper reaction chamber. The hydrogen outlet at the top of the upper reaction chamber is connected to the anode inlet of the fuel cell stack through a pipeline. The lower reaction chamber is equipped with a hydrolysis-type solid hydrogen storage material bed.

[0011] The pressure gauge is installed on the pipeline between the hydrogen outlet at the top of the upper reaction chamber and the anode inlet of the fuel cell stack, and is used to detect the hydrogen supply pressure of the upper reaction chamber.

[0012] The upper jacket is a hollow structure, fitted outside the upper reaction chamber. Its inner wall surface forms a heat exchange chamber with the outer wall surface of the reactor. The heat exchange chamber is connected to the cathode exhaust port of the fuel cell stack. Its bottom is provided with a condensate outlet and a condensate exhaust gas outlet.

[0013] The lower jacket is an annular water reservoir with an inlet and an outlet. It is fitted outside the lower reaction chamber, and its inner wall dimensions are adapted to the outer wall of the reactor. The inlet of the lower jacket is connected to the condensate outlet of the heat exchange chamber, and its outlet is connected to the lower reaction chamber through a water distribution device.

[0014] The water distribution device is used to transport the condensate in the lower jacket to the lower reaction chamber;

[0015] The spiral tube is located on the circumference of the reactor axis. Its upper section is located in the upper reaction chamber and its outlet extends into the hydrogen mixing cavity. Its lower section is located in the lower reaction chamber and is provided with hydrogen channels. Its middle part passes through the partition between the upper and lower reaction chambers and is sealed to the partition.

[0016] The control device is electrically connected to the pressure gauge and the water distribution device respectively, and is used to control the start and stop of the water distribution device according to the hydrogen supply pressure.

[0017] Furthermore, the water distribution device includes a water pump and a water distributor;

[0018] The water distributor includes one inlet pipe and multiple outlet pipes connected to the inlet pipe. Each outlet pipe is provided with multiple outlet holes. The multiple outlet pipes are evenly distributed at the bottom of the hydrolysis-type solid hydrogen storage material bed to provide it with a water source.

[0019] The inlet of the water pump is connected to the outlet of the lower jacket via a pipeline, and its outlet is connected to the inlet pipe of the water distributor.

[0020] Furthermore, the spiral tube is made of a high thermal conductivity metal, and a check valve is provided at the outlet of its upper section.

[0021] Furthermore, a pressure regulating valve is installed on the pipeline between the pressure gauge and the anode inlet of the fuel cell stack to stabilize the anode inlet pressure of the fuel cell stack;

[0022] The fuel cell stack is equipped with an anode inlet solenoid valve at the anode inlet and an anode outlet solenoid valve at the anode outlet.

[0023] Furthermore, the heat / mass self-balancing fuel cell also includes an air-cooled stack fan electrically connected to the control unit;

[0024] The heat exchange chamber is connected to the cathode exhaust port of the fuel cell stack via an air-cooled stack fan, which is located inside the heat exchange chamber and is used to introduce the cathode exhaust gas generated by the fuel cell stack into the heat exchange chamber.

[0025] Furthermore, a humidity sensor is also installed at the hydrogen outlet of the upper reaction chamber, and the humidity sensor is electrically connected to the control device.

[0026] Furthermore, the mass of the rare earth-based hydrogen storage alloy bed is... The mass of the hydrolysis-type solid hydrogen storage material bed is ,and and It is calculated using the following formula:

[0027] ;

[0028] ;

[0029] in, The total hydrogen molar rate of the fuel cell stack;

[0030] The target continuous operating time of the fuel cell stack;

[0031] The effective molar hydrogen storage density of the rare earth-based hydrogen storage alloy bed;

[0032] The effective molar hydrogen production density of the hydrolysis-type solid hydrogen storage material bed;

[0033] The molar ratio of hydrogen supplied by water electrolysis required for stable operation of a heat / mass self-balancing fuel cell under conditions of no external heat / mass input, and ;

[0034] The specific range of values ​​is calculated based on the thermal balance mathematical model and the mass balance mathematical model. The thermal balance mathematical model is as follows:

[0035] ;

[0036] in, This refers to the rated total output power of the fuel cell stack.

[0037] The electrical efficiency of the fuel cell stack;

[0038] The cathode exhaust gas heat distribution coefficient of the fuel cell stack;

[0039] The convective heat transfer efficiency of the heat exchange chamber in the upper jacket;

[0040] The thermal bridge efficiency of the spiral tube;

[0041] The hydrothermal decomposition constant of the hydrolysis-type solid hydrogen storage material bed;

[0042] The enthalpy of pyrolysis endothermic reaction of rare earth-based hydrogen storage alloy bed;

[0043] This refers to the natural heat dissipation power of the reactor at room temperature.

[0044] The mathematical model for mass balance is as follows:

[0045] ;

[0046] in, The water consumption to hydrogen production molar ratio for hydrolysis-type solid hydrogen storage material beds;

[0047] The excessive water injection coefficient for the project;

[0048] This refers to the condensate recovery rate.

[0049] Furthermore, this invention also provides a method for operating a heat / mass self-balancing fuel cell, which is characterized by including the following steps:

[0050] Step 1: Construct the above-mentioned self-balancing fuel cell (thermal / mass);

[0051] Step 2: The water distribution device is shut down by the control device. The rare earth hydrogen storage alloy bed in the upper reaction chamber is pyrolyzed to produce hydrogen. The hydrogen passes through the hydrogen outlet and pressure gauge at the top of the upper reaction chamber in sequence and then enters the anode of the fuel cell stack. The pressure gauge transmits the detected hydrogen supply pressure to the control device.

[0052] Step 3: Start the fuel cell stack. The high-temperature cathode exhaust gas generated is discharged into the heat exchange chamber between the upper jacket and the outer wall of the reactor.

[0053] Step 4: In the heat exchange chamber, the high-temperature cathode tail gas exchanges heat with the rare earth hydrogen storage alloy bed to provide heat to the rare earth hydrogen storage alloy bed. The condensate generated after the high-temperature cathode tail gas heat exchange flows into the lower jacket for storage through the condensate outlet, and the remaining condensate tail gas is discharged from the condensate tail gas outlet.

[0054] Step 5: During the operation of the fuel cell stack, the control device judges in real time whether the hydrogen supply pressure is greater than or equal to the preset pressure value and executes step 6; when the hydrogen supply pressure is less than the preset pressure value, it executes step 7.

[0055] Step 6: The control device shuts off the water distribution device;

[0056] Step 7: The control device starts the water distribution device, which transports the condensate in the lower jacket to the lower reaction chamber. The hydrolyzed solid hydrogen storage material bed begins to generate hydrogen. The hot hydrogen generated by the hydrolyzed solid hydrogen storage material bed enters the hydrogen mixing cavity through the hydrogen channel in the lower section of the spiral tube. After mixing with the hydrogen generated by the rare earth hydrogen storage alloy bed, it is transported to the anode of the fuel cell stack through the hydrogen outlet. During the transportation process in the spiral tube, the hot hydrogen generated by the hydrolyzed solid hydrogen storage material bed exchanges heat with the rare earth hydrogen storage alloy bed, providing it with heat and completing the thermal / mass self-balance regulation of the fuel cell.

[0057] Furthermore, step 7 also includes the following:

[0058] After the control device starts the water distribution device, the relative humidity of the mixed hydrogen at the hydrogen outlet is transmitted to the control device through the humidity sensor. When the relative humidity of the mixed hydrogen is greater than the preset humidity value, the control device controls the water distribution device to reduce the water supply to lower the relative humidity of the mixed hydrogen so that it does not exceed the preset humidity value.

[0059] Furthermore, the preset humidity value is ARH, where, .

[0060] Compared with the prior art, the present invention has the following beneficial technical effects:

[0061] 1. This invention discloses a heat / mass self-balancing fuel cell. A heat exchange chamber is constructed by installing an upper jacket over the upper reaction chamber, introducing the high-temperature, high-humidity exhaust gas generated at the fuel cell stack cathode into this chamber. The endothermic properties of the rare-earth-based hydrogen storage alloy bed during pyrolysis are utilized as a cold source to achieve in-situ condensation of the exhaust gas and recovery of moisture, thereby providing a reaction water source for the hydrolysis-type solid hydrogen storage material in the lower reaction chamber. Simultaneously, the sensible and latent heat released by the exhaust gas are absorbed by the rare-earth-based hydrogen storage alloy bed to maintain the pyrolysis reaction. The annular lower jacket over the lower reaction chamber also functions as a condensate storage unit and a thermal management unit for the hydrolysis reaction. This integrated structural design breaks down the heat and mass circulation barriers between the fuel cell stack and the dual-mode hydrogen source, significantly reducing system complexity and substantially decreasing equipment size and weight.

[0062] 2. This invention discloses a heat / mass self-balancing fuel cell. Through the design of an internal helical tube structure connecting the upper and lower reaction chambers, the high-temperature hydrogen gas generated by hydrolysis in the lower reaction chamber enters the helical tube through hydrogen channels in the lower section and is transported upwards. As it flows through the upper section of the helical tube, the helical tube wall acts as a high-thermal-conductivity heat bridge, efficiently transferring the intense heat released by the hydrolysis reaction and the sensible heat of the high-temperature hydrogen gas to the rare-earth-based hydrogen storage alloy bed, thus assisting in improving the pyrolysis hydrogen production rate. This design integrates the hydrogen collection channel and the internal heat exchanger function into one, achieving automatic matching of hydrolysis heat release and pyrolysis heat absorption in its physical structure, greatly improving the system's internal energy utilization rate.

[0063] 3. This invention discloses a heat / mass self-balancing fuel cell that utilizes a physical topology to allow the hydrolyzed wet hydrogen produced in the lower reaction chamber and the pyrolyzed dry hydrogen produced in the upper reaction chamber to naturally merge in the top mixing cavity. Without the need for an external humidifier or a complex humidity control subsystem, the system not only achieves a dynamic balance in the hydrogen supply rate but also dynamically adjusts the proportion of hydrogen produced from hydrolysis by controlling the water injection rate of the water distribution device. This allows for precise control of the temperature and humidity of the final output mixed hydrogen, ensuring it spontaneously operates within the optimal operating range of the proton exchange membrane. This effectively reduces the ohmic polarization resistance of the membrane and improves the electrochemical performance of the fuel cell stack.

[0064] 4. The present invention provides a heat / mass self-balancing fuel cell. By setting a pressure regulating valve in series in the gas supply pipeline, it can effectively suppress the pressure fluctuations that may occur during the dynamic switching or synergistic hydrogen production of dual-mode hydrogen sources, namely pyrolysis hydrogen production and water electrolysis hydrogen production. This ensures that the hydrogen pressure entering the anode of the fuel cell stack is strictly stable within the rated operating range, thereby ensuring the stable, safe and long-term operation of the stack under different load conditions.

[0065] 5. This invention discloses a method for operating a heat / mass self-balancing fuel cell. By establishing a two-way physical coupling mechanism of "exhaust gas heating - alloy heat absorption" and "exhaust gas condensation - water consumption for hydrolysis," the "waste heat" dissipated by the fuel cell stack is converted into energy to drive the pyrolysis reaction, and the "wastewater" emitted by the fuel cell stack is recovered and converted into materials for the hydrolysis reaction. This method achieves an absolute closed loop and cascaded utilization of energy and matter within the entire fuel cell system during execution, avoiding the dependence on external heat and water sources found in traditional systems.

[0066] 6. This invention discloses a method for operating a heat / mass self-balancing fuel cell. Relying on a pressure feedback mechanism, the water injection action in the reaction chamber is dynamically controlled by real-time monitoring of the hydrogen outlet pressure. When the pressure gauge detects that the hydrogen outlet pressure is lower than a preset threshold (indicating insufficient hydrogen supply from pyrolysis), water injection is automatically initiated to trigger a hydrolysis reaction to replenish hydrogen and heat. When the pressure rises back to or above the preset threshold, the water distribution device is shut off to stop hydrolysis. This established passive coordinated operation mechanism of "pyrolysis as the primary method and hydrolysis as a secondary method" enables dynamic self-balancing of the system's heat / mass without the need for complex algorithm intervention, significantly improving the net output power and overall fuel utilization rate of the fuel cell system. Attached Figure Description

[0067] Figure 1 This is a schematic diagram of the structure of an embodiment of the heat / mass self-balancing fuel cell of the present invention;

[0068] Figure 2 This is a schematic diagram of the spiral tube structure in an embodiment of the heat / mass self-balancing fuel cell of the present invention;

[0069] Figure 3 This is an axial cross-sectional view of the connection structure between the upper and lower jackets in a fuel cell embodiment of the present invention (only one side is shown).

[0070] The annotations in the attached figures are explained as follows:

[0071] 1. Fuel cell stack; 101. Stack anode inlet solenoid valve; 102. Stack anode outlet solenoid valve; 2. Air-cooled stack fan; 3. Upper jacket; 4. Reactor; 5. Rare earth hydrogen storage alloy bed; 6. Condensate exhaust outlet; 7. Condensate outlet; 8. Lower jacket; 9. Water pump; 10. Water distributor; 11. Hydrolysis-type solid hydrogen storage material bed; 12. Hydrogen channel; 13. Spiral tube; 14. Check valve; 15. Hydrogen outlet; 16. Pressure gauge; 17. Pressure regulator. Detailed Implementation

[0072] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0073] like Figure 1-3 As shown, this embodiment provides a thermal / mass self-balancing fuel cell, including a fuel cell stack 1, a thermal / mass self-balancing composite hydrogen storage device, and a control device.

[0074] The heat / mass self-balancing composite hydrogen storage device includes a reactor 4, an upper jacket 3, a lower jacket 8, an air-cooled fuel cell stack fan 2, a pressure gauge 16, a water distribution device, and a spiral pipe 13.

[0075] The upper jacket 3 is a hollow structure, which is fitted outside the upper reaction chamber. Its inner wall surface and the outer wall surface of the reactor 4 form a heat exchange chamber. The heat exchange chamber is connected to the cathode tail gas discharge port of the fuel cell stack 1. Its bottom is provided with a condensate outlet 7 and a condensate tail gas outlet 6. The cathode tail gas after heat exchange is discharged from the condensate tail gas outlet 6.

[0076] The fuel cell stack 1 is an air-cooled proton exchange membrane fuel cell stack. An air-cooled stack fan 2 is provided on the cathode side to provide cooling air to the fuel cell stack 1 and introduce the heat exchanged hot air into the heat exchange chamber. A stack anode inlet solenoid valve 101 is provided at the anode inlet of the fuel cell stack 1, and a stack anode outlet solenoid valve 102 is provided at the anode outlet to control the supply and purging of hydrogen.

[0077] Reactor 4 includes a vertically arranged cylindrical reactor shell, internally divided along the axial direction into a relatively independent upper reaction chamber and a lower reaction chamber. The upper reaction chamber contains a rare-earth-based hydrogen storage alloy bed 5, with a hydrogen mixing cavity formed between the top of the rare-earth-based hydrogen storage alloy bed 5 and the inner wall of the top of the upper reaction chamber. A hydrogen outlet 15 located at the top of the upper reaction chamber is connected to the anode inlet of the fuel cell stack 1 via a pipeline. The lower reaction chamber contains a hydrolysis-type solid hydrogen storage material bed 11. In this embodiment, the rare-earth-based hydrogen storage alloy bed 5 is a TiMn-based alloy, which has a high equilibrium hydrogen pressure (approximately 0.3~0.5 MPa) at room temperature and can spontaneously release hydrogen at room temperature. Furthermore, the average bed temperature during hydrogen release is <10℃. The hydrolysis-type solid hydrogen storage material bed 11 is a mixture of sodium borohydride (NaBH4) and a cobalt-based catalyst, used for hydrogen release through hydrolysis.

[0078] Pressure gauge 16 is installed on the pipeline between hydrogen outlet 15 at the top of the upper reaction chamber and anode inlet of fuel cell stack 1 to detect hydrogen supply pressure in the upper reaction chamber; pressure regulating valve 17 is installed on the pipeline between pressure gauge 16 and anode inlet of fuel cell stack 1 to stabilize anode inlet pressure of fuel cell stack 1.

[0079] The lower jacket 8 is an annular water reservoir with an inlet and an outlet. It is fitted outside the lower reaction chamber. Its inner wall dimensions are adapted to the outer wall of the reactor 4. The inlet of the lower jacket 8 is connected to the condensate outlet 7 of the heat exchange chamber, and its outlet is connected to the lower reaction chamber through a water distribution device.

[0080] The water distribution device is used to transport the condensate in the lower jacket 8 to the lower reaction chamber. The water distribution device includes a water pump 9 and a water distributor 10. The water distributor 10 includes one inlet pipe and multiple outlet pipes connected to the inlet pipe. Each outlet pipe has multiple outlet holes. The multiple outlet pipes are evenly distributed at the bottom of the hydrolysis-type solid hydrogen storage material bed 11 to provide it with a water source. The inlet of the water pump 9 is connected to the outlet of the lower jacket 8 through a pipe, and its outlet is connected to the inlet pipe of the water distributor 10. In this embodiment, the water pump 9 is a peristaltic pump. The water distributor 10 is located at the bottom of the lower reaction chamber and is evenly arranged at the bottom of the lower reaction chamber using a porous branch pipe structure. It is used to evenly distribute the condensate to the hydrolysis-type solid hydrogen storage material bed 11 to ensure the uniformity of the hydrolysis reaction.

[0081] The spiral tube 13 is located around the axis of the reactor 4. Its upper section is located in the upper reaction chamber, and its outlet extends into the hydrogen mixing cavity. Its lower section is located in the lower reaction chamber, and a hydrogen channel 12 is provided on the lower section. The middle part passes through the partition between the upper and lower reaction chambers and is sealed to the partition. The spiral tube 13 is made of a high thermal conductivity metal, and a check valve 14 is provided at the outlet of its upper section to prevent hydrogen backflow. In this embodiment, the spiral tube 13 is made of copper, which has good thermal conductivity.

[0082] The control device is electrically connected to the pressure gauge 16 and the water distribution device respectively, and is used to control the start and stop of the water distribution device according to the hydrogen supply pressure. That is, the control device is electrically connected to the water pump 9.

[0083] The heat exchange chamber is connected to the cathode exhaust port of the fuel cell stack 1 via an air-cooled stack fan 2, which is located inside the heat exchange chamber to introduce the high-temperature, high-humidity cathode exhaust gas generated by the fuel cell stack 1 into the heat exchange chamber. The air-cooled stack fan 2 is nested with the reactor 4, allowing the exhaust gas from the fuel cell stack 1 to be directly introduced into the heat exchange chamber, reducing heat loss.

[0084] A humidity sensor is also installed at the hydrogen outlet 15 of the upper reaction chamber, and the humidity sensor is electrically connected to the control device.

[0085] In this embodiment, considering the space constraints of portable applications, the external envelope dimensions of reactor 4 are preset to be: total height 300mm and diameter 100mm. Based on these preset dimensions and the heat transfer coefficient of stainless steel, the natural heat dissipation power of reactor 4 at room temperature (e.g., 25℃) is calculated to be 28W.

[0086] The parameters of the selected hydrogen storage material were obtained: the effective molar hydrogen storage density of the TiMn alloy in the upper reaction chamber is 0.00876 mol / g, and the apparent bulk density is approximately 3.5 g / cm³. 3 The effective molar hydrogen production density of the NaBH4 mixture in the lower reaction chamber was 0.0054 mol / g, and the apparent bulk density was approximately 1.2 g / cm³. 3 .

[0087] Initially, a small amount of initial deionized water (approximately 50 mL, serving as a start-up water pad) is pre-placed in the lower jacket 8 of reactor 4. The TiMn-based alloy in the upper reaction chamber has a high equilibrium hydrogen pressure (approximately 0.3~0.5 MPa) at room temperature, which is greater than the initial pressure inside reactor 4 (0.1 MPa at atmospheric pressure). The spontaneously released initial hydrogen gas can raise the anode of fuel cell stack 1 to the operating pressure (0.05 MPa) within 0~1 min, meeting the rapid start-up requirements of fuel cell stack 1.

[0088] During the stable operation phase, this invention achieves dynamic self-equilibrium of heat and mass based on a rigorous mathematical model:

[0089] Rated total output power of fuel cell stack 1 Electrical efficiency The average operating voltage of a single cell in fuel cell stack 1 The Faraday constant F = 96485 C / mol. According to electrochemical theory, the total hydrogen molar consumption rate of fuel cell stack 1... It corresponds strictly to the theoretical water production molar rate and is independent of the number of cells in series, directly derived from the baseline term. Decision. The total theoretical water production (i.e. hydrogen consumption) rate of fuel cell stack 1 is determined according to... The calculation yielded a total theoretical water production (i.e. hydrogen consumption) rate of approximately 0.00166 mol / s.

[0090] (1) The heat balance calculation process is as follows:

[0091] The dynamic self-equilibrium of a heat / mass self-balancing fuel cell is primarily governed by thermodynamic boundaries, and its thermal equilibrium mathematical model is as follows:

[0092] ;

[0093] in, The total hydrogen molar rate of fuel cell stack 1;

[0094] Let W be the total output power of fuel cell stack 1, and let W be the electrical output load.

[0095] The electrical efficiency of fuel cell stack 1 determines the amount of waste heat generated by fuel cell stack 1 (typically between 40% and 60% for proton exchange membrane fuel cells).

[0096] The cathode exhaust gas heat distribution coefficient of fuel cell stack 1; thermal management characteristics of fuel cell stack 1 (in air-cooled stacks, the proportion of heat carried away by the cathode exhaust gas is generally 20%-40%).

[0097] The convective heat transfer efficiency of the heat exchange chamber in the upper jacket 3;

[0098] The thermal bridge conductivity of the spiral tube 13;

[0099] The hydrothermal decomposition constant of the hydrolysis-type solid hydrogen storage material bed 11 is (thermodynamic constant, );

[0100] The enthalpy of thermal decomposition for rare-earth hydrogen storage alloy bed 5 is given by (thermodynamic constant). );

[0101] The intensity of the hydrolysis reaction is dynamically adjusted based on the molar ratio of hydrogen donated for hydrolysis. ;

[0102] This represents the natural heat dissipation power of reactor 4 at room temperature.

[0103] The left side of the inequality represents the effective heat source: the total waste heat of the fuel cell stack is 200W, and the proportion of sensible heat carried by the cathode exhaust gas is... =30%. Due to the large convective thermal resistance at the metal wall surface during gas-to-solid heat transfer, the effective gas-wall heat transfer efficiency of the upper jacket is... =60%, then the effective recovery of cathode tail gas for heating is .

[0104] The right side of the equation represents the heat absorption and dissipation loads: enthalpy of heat absorption in TiMn alloy. If hydrogen supply relies entirely on pyrolysis (0.1 mol / min), the theoretical endothermic power required is 50 W. Simultaneously, the natural heat dissipation of the metal reactor 4 (300 mm high, 100 mm diameter) at room temperature must be overcome. ≈28W. Obviously, the 36W of cathode exhaust heat alone is insufficient to sustain the operation of fuel cell stack 1.

[0105] Therefore, a hydrolysis reaction must be introduced as an internal heat source, and the hydrolysis heat release constant of NaBH4 is... Thermal conductivity of spiral tube The above heat balance equation is solved by a PID controller (i.e., control device) to find the self-balancing optimum, and finally the steady-state control strategy is locked as follows: hydrogen supply from hydrolysis accounts for a certain percentage. (i.e., 0.6 L / min), with pyrolysis accounting for 73% of hydrogen supply.

[0106] At this point, a heat recalculation is performed: the effective upward heat transfer from hydrolysis is 0.1 × 27% × 75000 × 0.85 / 60 ≈ 28.7 W. The total effective heat transfer is 36 W + 28.7 W = 64.7 W. The endothermic power required to maintain a 73% pyrolysis rate is 0.1 × 73% × 30000 / 60 ≈ 36.5 W. This results in a heat surplus of approximately 28.2 W, perfectly offsetting the [heat transfer deficit]. Thermal equilibrium was achieved.

[0107] (2) Quality balance accounting

[0108] Mathematical model of mass balance:

[0109] ;

[0110] Further simplification yields:

[0111] ;

[0112] Where F is the Faraday constant, 96485 C / mol;

[0113] The average voltage of a single cell is a dynamic parameter reflecting the operating efficiency of fuel cell stack 1.

[0114] The water-to-hydrogen molar ratio for hydrolysis represents the theoretical number of water molecules required to produce 1 mol of hydrogen gas. For example, the sodium borohydride system. Aluminum hydrolysis system ;

[0115] The excessive water injection coefficient for the project is a safety parameter to prevent clogging. To prevent high-concentration crystallization of by-products from clogging the bed, it is usually set between 1.5 and 3.

[0116] Condensate recovery rate;

[0117] This is the molar mass of water.

[0118] Left side of the equation (condensate recovery rate): According to Faraday's law of electrolysis, the fuel cell generates current. Since 2 mol of electrons need to be transferred to produce 1 mol of water, the theoretical water production molar rate of fuel cell stack 1 is... Multiply by the molar mass of water Obtain the mass rate, then multiply it by the condensate recovery rate. This refers to the actual recoverable liquid water rate of a heat / mass self-balancing fuel cell.

[0119] The right side of the equation (water consumption rate due to hydrolysis): The percentage needs to be provided. The hydrogen hydrolysis rate corresponds to the hydrogen consumption molar rate as follows: Multiply this by the intrinsic water consumption and hydrogen production molar ratio of the hydrolysis material. The theoretical water consumption molar rate is obtained; then multiplied by the engineering water injection excess coefficient. and molar mass That is, the boundary of the actual water injection rate required to maintain the hydrolysis reaction in a heat / mass self-balancing fuel cell.

[0120] After establishing the thermal balance, it was determined that the proportion of hydrogen donated by water electrolysis must reach a certain level. After reaching 27%, it is necessary to verify whether the water recovered inside the upper jacket 3 is sufficient to support the hydrolysis consumption. The water balance must meet the constraint criteria:

[0121] ;

[0122] Since the average temperature of the rare-earth-based hydrogen storage alloy bed 5 during the hydrogen release process of the pyrolysis material is <10℃, the theoretical maximum condensation efficiency of the cathode tail gas at 65°C and 50%RH is approximately 90.2% when forced convection heat transfer is performed at this temperature. However, due to the micro-droplet entrainment and escape phenomenon during the gas-liquid separation process of the passive jacketed condenser, the actual condensate recovery rate of the jacket 3 in the system is approximately 70%, so the actual condensate recovery rate is... The concentration was 1.26 g / min (1.26 mL / min).

[0123] The lower reaction chamber uses sodium borohydride as a material, and its theoretical water consumption to hydrogen production molar ratio is... To prevent the crystallization of reaction byproducts, an excess water injection coefficient is set for the project. =2.0. Substituting the parameters derived from thermodynamics into the moisture constraint condition: 0.70≥27%×1×2.0 (i.e. 0.7≥0.54), the inequality holds significantly.

[0124] The actual physical characteristics are as follows: actual water consumption for hydrolysis = 1.8 g / min × 27% × 1 × 2.0 ≈ 0.97 ml / min. This consumption is significantly less than the actual recovery rate of 1.26 mL / min. The system produces approximately 0.29 mL / min of net water, with excess water continuously accumulating in the lower jacket.

[0125] In summary, this system achieves dynamic self-balancing without external energy or water input under a rated operating condition of 200W.

[0126] Mass of the TiMn alloy bed in the upper reaction chamber:

[0127]

[0128]

[0129] Based on the above calculations of mass and material bulk density, the required TiMn alloy volume is approximately 143 cm³. 3 The volume of the NaBH4 mixture is approximately 250 cm³. 3 The pre-designed reactor 4 (diameter 100mm, effective inner diameter approximately 80mm after deducting jacket and pipe thickness) has an effective internal volume of approximately 750cm³ for its single-sided reaction chamber (height 150mm). 3 The reactor must be able to fully accommodate the hydrogen storage material of the calculated mass, with sufficient space for hydrogen expansion and permeation to meet the requirements of thermal and mass balance operation. If the volume verification fails (i.e., the volume of any required material exceeds the preset effective volume inside the single-sided reaction chamber), it indicates that the current preset dimensions cannot meet the set rated power and operating time requirements. In this case, the control or design strategy needs to be iteratively corrected: by increasing the external envelope size of the preset reactor 4, reducing the target continuous operating time, reducing the rated total power of the stack, or replacing it with a material with a higher hydrogen storage / production density, and recalculating the thermal / mass balance until the volume verification passes.

[0130] The present invention also provides a method for operating a heat / mass self-balancing fuel cell, comprising the following steps:

[0131] Step 1: Construct the above-mentioned self-balancing fuel cell in terms of heat and mass.

[0132] Step 2: The water distribution device is shut down by the control device. The rare earth hydrogen storage alloy bed 5 in the upper reaction chamber is pyrolyzed to produce hydrogen. The hydrogen enters the anode of the fuel cell stack 1 after passing through the hydrogen outlet 15 at the top of the upper reaction chamber and the pressure gauge 16. The pressure gauge 16 transmits the detected hydrogen supply pressure to the control device.

[0133] Step 3: Start the fuel cell stack 1. The high-temperature cathode exhaust gas generated by it is discharged into the heat exchange chamber between the upper jacket 3 and the outer wall of the reactor 4.

[0134] Step 4: In the heat exchange chamber, the high-temperature cathode exhaust gas exchanges heat with the rare earth hydrogen storage alloy bed 5 to provide heat to the rare earth hydrogen storage alloy bed 5. The condensate generated after the high-temperature cathode exhaust gas heat exchange flows into the lower jacket 8 through the condensate outlet 7 for storage, and the remaining condensate exhaust gas is discharged from the condensate exhaust gas outlet 6.

[0135] Step 5: During the operation of fuel cell stack 1, the control device determines in real time whether the hydrogen supply pressure is greater than or equal to the preset pressure value, and executes step 6; when the hydrogen supply pressure is less than the preset pressure value, it executes step 7.

[0136] Step 6: The control device shuts down the water distribution device.

[0137] Step 7: The control device activates the water distribution device, allowing condensate in the lower jacket 8 to be transported to the lower reaction chamber. The hydrolyzed solid hydrogen storage material bed 11 begins to generate hydrogen. This hydrogen enters the spiral tube 13 through the hydrogen channel 12 and is transported to the hydrogen mixing cavity. After mixing with the hydrogen generated by the rare earth-based hydrogen storage alloy bed 5, it is transported to the anode of the fuel cell stack 1 through the hydrogen outlet 15. During its transport within the spiral tube 13, the hot hydrogen generated by the hydrolyzed solid hydrogen storage material bed 11 exchanges heat with the rare earth-based hydrogen storage alloy bed 5, providing it with heat to increase the hydrogen production of the rare earth-based hydrogen storage alloy bed 5. Simultaneously, the humidity sensor transmits the relative humidity of the mixed hydrogen at the hydrogen outlet 15 to the control device. When the relative humidity of the mixed hydrogen exceeds a preset humidity value, the control device reduces the water flow of the water distribution device to lower the relative humidity of the mixed hydrogen, thus completing the thermal / mass self-balancing regulation of the fuel cell. In this embodiment, the preset humidity value is 80%.

[0138] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A heat / mass self-balancing fuel cell, characterized in that: Includes fuel cell stack (1), thermal / mass self-balancing composite hydrogen storage device and control device; The heat / mass self-balancing composite hydrogen storage device includes a reactor (4), an upper jacket (3), a lower jacket (8), a pressure gauge (16), a water distribution device, and a spiral tube (13). The reactor (4) includes a relatively independent upper reaction chamber and a lower reaction chamber. The upper reaction chamber is provided with a rare earth hydrogen storage alloy bed (5). A hydrogen mixing cavity is formed between the top of the rare earth hydrogen storage alloy bed (5) and the inner wall of the top of the upper reaction chamber. The hydrogen outlet (15) set at the top of the upper reaction chamber is connected to the anode inlet of the fuel cell stack (1) through a pipeline. The lower reaction chamber is provided with a hydrolysis-type solid hydrogen storage material bed (11). The pressure gauge (16) is installed on the pipeline between the hydrogen outlet (15) at the top of the upper reaction chamber and the anode inlet of the fuel cell stack (1) to detect the hydrogen supply pressure of the upper reaction chamber; The upper jacket (3) is a hollow structure and is fitted outside the upper reaction chamber. Its inner wall surface forms a heat exchange chamber with the outer wall surface of the reactor (4). The heat exchange chamber is connected to the cathode tail gas discharge port of the fuel cell stack (1). Its bottom is provided with a condensate outlet (7) and a condensate tail gas outlet (6). The lower jacket (8) is an annular water reservoir with an inlet and an outlet. It is fitted outside the lower reaction chamber. Its inner wall size is adapted to the outer wall of the reactor (4). The inlet of the lower jacket (8) is connected to the condensate outlet (7) of the heat exchange chamber, and its outlet is connected to the lower reaction chamber through a water distribution device. The water distribution device is used to transport the condensate in the lower jacket (8) to the lower reaction chamber; The spiral tube (13) is located on the circumference of the axis of the reactor (4). Its upper section is located in the upper reaction chamber and the outlet of the upper section extends into the hydrogen mixing cavity. Its lower section is located in the lower reaction chamber and is provided with a hydrogen channel (12). Its middle part passes through the partition between the upper and lower reaction chambers and is sealed to the partition. The control device is electrically connected to the pressure gauge (16) and the water distribution device respectively, and is used to control the start and stop of the water distribution device according to the hydrogen supply pressure.

2. The self-balancing fuel cell according to claim 1, characterized in that: The water distribution device includes a water pump (9) and a water distributor (10). The water distributor (10) includes one inlet pipe and multiple outlet pipes that are connected to the inlet pipe. Each outlet pipe is provided with multiple outlet holes. The multiple outlet pipes are evenly distributed at the bottom of the hydrolysis-type solid hydrogen storage material bed (11) to provide it with a water source. The inlet of the water pump (9) is connected to the outlet of the lower jacket (8) through a pipeline, and its outlet is connected to the inlet pipe of the water distributor (10).

3. The self-balancing fuel cell according to claim 1, characterized in that: The spiral tube (13) is made of a high thermal conductivity metal material, and a check valve (14) is provided at the outlet of its upper section.

4. The self-balancing fuel cell according to claim 1, characterized in that: A pressure regulating valve (17) is provided on the pipeline between the pressure gauge (16) and the anode inlet of the fuel cell stack (1) to stabilize the anode inlet pressure of the fuel cell stack (1); The fuel cell stack (1) is provided with a stack anode inlet solenoid valve (101) at the anode inlet and a stack anode outlet solenoid valve (102) at the anode outlet.

5. The self-balancing fuel cell according to claim 1, characterized in that: It also includes an air-cooled fuel cell stack fan (2) that is electrically connected to the control device; The heat exchange chamber is connected to the cathode exhaust port of the fuel cell stack (1) through an air-cooled stack fan (2), and the air-cooled stack fan (2) is located in the heat exchange chamber to introduce the cathode exhaust gas generated by the fuel cell stack (1) into the heat exchange chamber.

6. The self-balancing fuel cell according to claim 1, characterized in that: A humidity sensor is also installed at the hydrogen outlet (15) of the upper reaction chamber, and the humidity sensor is electrically connected to the control device.

7. The self-balancing fuel cell according to claim 1, characterized in that, The mass of the rare earth-based hydrogen storage alloy bed (5) is The mass of the hydrolysis-type solid hydrogen storage material bed (11) is ,and and It is calculated using the following formula: ； ； in, The total hydrogen molar rate of the fuel cell stack (1); The target continuous operating time of the fuel cell stack (1); The effective molar hydrogen storage density of the rare earth-based hydrogen storage alloy bed (5); The effective molar hydrogen production density of the hydrolysis-type solid hydrogen storage material bed (11); The molar ratio of hydrogen supplied by water electrolysis required for stable operation of a heat / mass self-balancing fuel cell under conditions of no external heat / mass input, and ; The range of values ​​is calculated based on the thermal balance mathematical model and the mass balance mathematical model. The thermal balance mathematical model is as follows: ； in, The rated total output power of the fuel cell stack (1); The electrical efficiency of the fuel cell stack (1); is the cathode exhaust heat distribution coefficient of the fuel cell stack (1); The convective heat transfer efficiency of the heat exchange chamber of the upper jacket (3); The thermal bridge thermal conductivity of the spiral tube (13) is . The hydrothermal decomposition constant of the hydrolysis-type solid hydrogen storage material bed (11); The enthalpy of thermal decomposition of the rare earth hydrogen storage alloy bed (5) is given. The natural heat dissipation power of reactor (4) at room temperature; The mathematical model for mass balance is as follows: ； in, The water consumption and hydrogen production molar ratio of the hydrolysis-type solid hydrogen storage material bed (11); The excessive water injection coefficient for the project; This refers to the condensate recovery rate.

8. A method for operating a self-balancing heat / mass fuel cell, characterized in that, Includes the following steps: Step 1: Construct a self-balancing fuel cell according to any one of claims 1-7; Step 2: The water distribution device is shut down by the control device. The rare earth hydrogen storage alloy bed (5) in the upper reaction chamber is pyrolyzed to produce hydrogen. The hydrogen enters the anode of the fuel cell stack (1) after passing through the hydrogen outlet (15) and pressure gauge (16) at the top of the upper reaction chamber. The pressure gauge (16) transmits the detected hydrogen supply pressure to the control device. Step 3: Start the fuel cell stack (1), and the high-temperature cathode exhaust gas generated by it is discharged into the heat exchange chamber between the upper jacket (3) and the outer wall of the reactor (4); Step 4: In the heat exchange chamber, the high-temperature cathode tail gas exchanges heat with the rare earth hydrogen storage alloy bed (5) to provide heat to the rare earth hydrogen storage alloy bed (5), and the condensate generated after the high-temperature cathode tail gas heat exchange flows into the lower jacket (8) through the condensate outlet (7) for storage, and the remaining condensate tail gas is discharged from the condensate tail gas outlet (6). Step 5: During the operation of the fuel cell stack (1), the control device judges in real time whether the hydrogen supply pressure is greater than or equal to the preset pressure value and executes step 6; when the hydrogen supply pressure is less than the preset pressure value, it executes step 7. Step 6: The control device shuts off the water distribution device; Step 7: The control device starts the water distribution device, so that the condensate in the lower jacket (8) is transported to the lower reaction chamber. Hydrogen gas is generated in the hydrolysis solid hydrogen storage material bed (11). The hot hydrogen gas generated by the hydrolysis solid hydrogen storage material bed (11) enters the hydrogen mixing cavity through the hydrogen channel (12) in the lower section of the spiral tube (13). After mixing with the hydrogen gas generated by the rare earth hydrogen storage alloy bed (5), it is transported to the anode of the fuel cell stack (1) through the hydrogen outlet (15). During the transportation process in the spiral tube (13), the hot hydrogen gas generated by the hydrolysis solid hydrogen storage material bed (11) exchanges heat with the rare earth hydrogen storage alloy bed (5) to provide heat and complete the thermal / mass self-balance regulation of the fuel cell.

9. The method for operating a self-balancing fuel cell according to claim 8, characterized in that, Step 7 also includes the following: After the control device starts the water distribution device, the relative humidity of the mixed hydrogen at the hydrogen outlet (15) is transmitted to the control device through the humidity sensor. When the relative humidity of the mixed hydrogen is greater than the preset humidity value, the control device controls the water distribution device to reduce the water supply to lower the relative humidity of the mixed hydrogen so that it does not exceed the preset humidity value.

10. The method for operating a self-balancing fuel cell according to claim 8, characterized in that: The preset humidity value is ARH, where... .

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