System modeling method for proton exchange membrane hydrogen production through water electrolysis and ammonia synthesis through deep cooling air separation

Abstract

The invention discloses a system modeling method for hydrogen production through water electrolysis of a proton exchange membrane and ammonia synthesis through cryogenic air separation. The system modeling step comprises the step of establishing four mutually connected subsystem models, including a solar photovoltaic power generation subsystem model, a water electrolysis hydrogen production subsystem model, a cryogenic air molecule system model and a synthesis ammonia subsystem model. The invention provides a process for producing hydrogen by electrolyzing water through a photovoltaic-driven proton exchange membrane electrolytic cell, producing nitrogen by cryogenic air separation and coupling ammonia synthesis, so that ammonia-heat co-production is realized, the production efficiency and sustainability of green ammonia are remarkably improved, and a feasible scheme is provided for producing ammonia from renewable energy sources. The steady-state simulation of proton exchange membrane electrolytic cell hydrogen production and deep cooling air separation cooperative ammonia production based on solar photovoltaic driving is realized. The simulation model method can quickly predict the system performance at low cost, provides a quantitative basis for reactor structure optimization and working condition adjustment, further reduces a large amount of time and economic cost consumed by engineering trial and error, and improves the efficiency of system design optimization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy, and specifically proposes a system modeling method for hydrogen production by proton exchange membrane electrolyzer driven by solar photovoltaic and ammonia production by deep cooling air separation. BACKGROUND

[0002] Due to global environmental challenges and the intensification of the greenhouse effect, energy reform is imperative. Among all energies, solar energy is the cleanest and most pollution-free renewable energy. The entire production process of hydrogen production by solar energy coupled with proton exchange membrane electrolysis has almost no carbon emissions, meeting the requirements of green environmental protection and sustainable development. With the decline of renewable energy costs, proton exchange membrane electrolysis has become an important method to achieve zero-carbon hydrogen production. Using green hydrogen (i.e., hydrogen produced by electrolysis of water) combined with nitrogen to synthesize ammonia can produce ammonia without relying on fossil fuels. This provides a technical approach for low-carbon or zero-carbon ammonia production.

[0003] There are still some problems in the chemical energy utilization link of converting solar energy into hydrogen and ammonia. First, solar energy is unstable, and the power consumption of proton exchange membrane electrolysis cannot be coupled with solar energy in real time, resulting in that solar energy cannot be fully utilized. In addition, the traditional hydrogen ammonia production process requires high temperature (about 400-500℃) and high pressure (about 150-300atm) conditions, which requires a large amount of high-grade energy. Therefore, if an ammonia production system modeling method that combines efficient ammonia production with green environmental protection can be proposed, a large amount of experimental time will be saved, and the production process can be optimized and adjusted.

[0004] The efficient and low-carbon ammonia cogeneration coupling system modeling method proposed in the application aims to reduce energy consumption while producing stable ammonia. By establishing a simulation model, the performance of the system can be effectively predicted at a lower economic cost, and the influence of different operating conditions on the performance can be studied. Based on this, the overall design of the system model can be further optimized to find the optimal operating condition, thereby improving the efficiency of the system. This method is mainly applied to the design and development stage of the multi-cogeneration system, and provides ideas and methods for the optimization design of the subsequent system. SUMMARY

[0005] The purpose of the application is to provide a system modeling method for hydrogen production by water electrolysis using proton exchange membrane electrolyzer and ammonia synthesis by deep cooling air separation based on photovoltaic power generation. It mainly includes the establishment method of the solar photovoltaic power generation system, the establishment method of the hydrogen production subsystem by water electrolysis, the establishment method of the deep cooling air separation subsystem, and the establishment method of the ammonia synthesis subsystem.

[0006] The system modeling method for hydrogen production by water electrolysis using proton exchange membrane and ammonia synthesis by deep cooling air separation includes the following steps for model construction:

[0007] S1: Establishing a solar photovoltaic power generation system: beneficial to the solar photovoltaic panel assembly, inputting solar radiation values to obtain photovoltaic power, wherein the solar photovoltaic panel assembly control equation includes electrical efficiency and thermal efficiency.

[0008] S2: Building a hydrogen production subsystem model, which includes the mathematical constraint model of the proton exchange membrane electrolyzer, the cooling water heat exchanger, the anode separator, and the cathode separator. By inputting the electrical energy given by the photovoltaic power generation system model simulation, the mass flow rate, temperature, and pressure of the produced hydrogen gas are obtained.

[0009] S3: The mathematical constraint model of the proton exchange membrane electrolyzer includes mass conservation, voltage calculation, and energy conservation equations. In the mathematical model of the proton exchange membrane electrolyzer, the electrical energy given by the photovoltaic power generation system model is inputted, and the mass flow rate, temperature, and pressure of the hydrogen gas produced by the proton exchange membrane electrolyzer are obtained.

[0010] S4: According to the proton exchange membrane electrolyzer model, a separator model is built. The anode separator model is constrained by the phase equilibrium equation, and the separation efficiency is solved based on the anode separation temperature, pressure, and the physical property parameters of oxygen and water. Then, based on the cooling water and the physical property parameters of the mixed gas, the waste heat used by the cooling water heat exchanger model is obtained by inputting the final temperature of the cooling water.

[0011] S5: Building a deep cooling air separation system model, which includes the mathematical constraint model of the air compressor, the cooling water heat exchanger, the air expander, and the nitrogen separator. By inputting the electrical energy given by the photovoltaic power generation system model, the mass flow rate, temperature, and pressure of the produced nitrogen gas are obtained.

[0012] S6: In order to simulate the process of producing ammonia gas from nitrogen and hydrogen, a synthetic ammonia subsystem model is built, which adopts the Haber-Bosch process to produce ammonia gas. The synthetic ammonia subsystem model includes the mathematical constraint model of the synthetic ammonia reactor, the heat pump, the ammonia separator, and the heat exchanger. By inputting the mass flow rate, temperature, and pressure of hydrogen and nitrogen, and the electrical energy given by the photovoltaic power generation system model, the mass flow rate, temperature, and pressure of the final produced ammonia gas are obtained.

[0013] S7: The synthetic ammonia reactor adopts a three-layer catalytic bed mathematical model, which includes the reactor reaction rate constraint equation, the reactor structure parameters, the reaction kinetics parameters, and the operating conditions. By inputting the required temperature and pressure for the reaction, as well as the physical property parameters of the reaction inside the reactor, including the partial pressure of hydrogen and oxygen, and the reaction equilibrium constant, the ammonia generation rate in the final model, as well as the temperature and pressure of the ammonia gas at that time, are obtained.

[0014] S8: Constructing the heat pump model according to the synthetic ammonia reactor model. The heat pump model is constrained by the heat calculation formula, and the temperature of the hydrogen-nitrogen mixed gas after heating is obtained by inputting the heating heat energy. The ammonia gas separator constraint model is solved based on the separation temperature, pressure, and based on the physical property parameters of ammonia gas to solve the separation efficiency. The cooling water heat exchanger model constraint is constrained by the energy conservation equation, and the temperature finally reached by inputting the heat stream is calculated to calculate the waste heat used by the cooling water heat exchanger.

[0015] The solar photovoltaic power generation panel assembly control equation includes electrical efficiency and thermal efficiency:

[0016] (1) Electrical efficiency equation:

[0017] P el =N PV / T η PV / T，e τGA P V / T (1)

[0018] (2) Thermal efficiency equation:

[0019] Q th =N PV / T GA PV / T τη PV / T，t (1-η PV / T，e ) (2)

[0020] The proton exchange membrane electrolyzer simulation model control equation includes:

[0021] (1) Mass conservation equation:

[0022]

[0023] (2) Voltage calculation equation:

[0024] V cell =V ocv +V act +V ohm +V con (4)

[0025] (3) Energy conservation equation:

[0026]

[0027] The electrical efficiency of the electrolyzer is calculated by the following formula:

[0028]

[0029] The three-layer catalytic bed mathematical model comprises a reaction rate constraint equation, reactor structure parameters, reaction kinetics parameters and operating conditions. By inputting the required temperature, pressure and internal reaction property parameters (hydrogen and oxygen partial pressures and reaction equilibrium constant) of the reactor, the final model can obtain the ammonia generation rate and the temperature and pressure of the ammonia at this time.

[0030] The system modeling method for hydrogen production by water electrolysis and ammonia synthesis by cryogenic air separation includes four interconnected subsystem models, including a solar photovoltaic power generation system model (including a solar photovoltaic panel assembly), a water electrolysis hydrogen production subsystem model (powered by the solar photovoltaic panel assembly, including a proton exchange membrane electrolyzer, a cooling water heat exchanger, an anode separator and a multi-stage cathode separator, realizing hydrogen production and water resource recycling), a cryogenic air separation subsystem model (powered by the solar photovoltaic panel assembly, including a compressor, a heat exchanger, an expander and a separator, separating high-purity nitrogen based on the ideal gas state equation), and an ammonia synthesis subsystem model (adopting the Haber-Bosch process, integrating a compressor, a heat pump, a three-layer gradient cooling catalytic bed reactor and a multi-stage separation / recycling device model, realizing ammonia synthesis and efficient recovery of unreacted gas).

[0031] The modeling method proposes to produce hydrogen by water electrolysis and nitrogen by cryogenic air separation through a proton exchange membrane electrolyzer driven by photovoltaic power, coupled with an ammonia synthesis process, to realize ammonia cogeneration and significantly improve the efficiency and sustainability of green ammonia production, providing a feasible solution for renewable energy-based ammonia production. The simulation model realizes stable-state simulation of hydrogen production by a proton exchange membrane electrolyzer and ammonia synthesis by cryogenic air separation driven by solar photovoltaic power. The simulation model can quickly and low-cost predict system performance, providing quantitative basis for reactor structure optimization and working condition adjustment, thereby reducing the large amount of time and economic cost consumed by engineering trial and error and improving the efficiency of system design optimization.

[0032] The characteristics and benefits of the present application are as follows: (1) The system modeling method proposed in the present application precisely models each module of the green ammonia production system, realizes zero fossil energy dependence throughout the whole process, directly couples renewable energy with the ammonia synthesis process, breaks through the high carbon emission bottleneck of traditional ammonia synthesis, and provides a decarbonization solution that can be implemented in the chemical industry. (2) By establishing a precise model for multi-subsystem collaborative simulation, the influence of photovoltaic output fluctuation on the performance of each subsystem is accurately quantified. The model can dynamically optimize the energy consumption distribution of hydrogen production by electrolysis and nitrogen production by air separation, realize flexible matching of unstable solar energy and rigid ammonia synthesis process, and solve the core bottleneck of large-scale ammonia production by intermittent renewable energy. (3) The proposed modeling method not only reduces the commercialization risk, but also forms a modular design paradigm, providing key technical support for the engineering design of photovoltaic hydrogen synthesis ammonia integrated plants and accelerating the industrialization process of green ammonia. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1The system architecture diagram for modeling the method of the present application.

[0034] Figure 2 The graph of the change of hydrogen production and ammonia production with electrolytic cell input power established for the example of the present application.

[0035] Figure 3 The graph of the relationship between reactor bed temperature and conversion rate established for the example of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application more clear, the method steps of the present application are further described below through specific examples and the accompanying drawings. It should be noted that the present examples are narrative and not limiting, and do not limit the protection scope of the present application.

[0037] The system modeling method for hydrogen production by water electrolysis and ammonia synthesis by cryogenic air separation includes the establishment of a solar photovoltaic power generation system, a hydrogen production by water electrolysis subsystem, a cryogenic air separation subsystem, and an ammonia synthesis subsystem. The method steps for model construction are as follows:

[0038] S1: Establishment of a solar photovoltaic power generation system: a solar photovoltaic panel assembly is used to input solar radiation values to obtain photovoltaic power, wherein the solar photovoltaic panel assembly control equation includes electrical efficiency and thermal efficiency.

[0039] S2: Construction of a hydrogen production by water electrolysis subsystem model, which includes mathematical constraint models of a proton exchange membrane electrolytic cell, a cooling water heat exchanger, an anode separator, and a cathode separator. By inputting the electrical energy given by the photovoltaic power generation system model simulation, the mass flow rate, temperature, and pressure of the produced hydrogen gas are obtained.

[0040] S3: The mathematical constraint model of the proton exchange membrane electrolytic cell includes mass conservation, voltage calculation, and energy conservation equations. In the mathematical model of the proton exchange membrane electrolytic cell, the electrical energy given by the photovoltaic power generation system model is input to obtain the mass flow rate, temperature, and pressure of the hydrogen gas produced by the proton exchange membrane electrolytic cell.

[0041] S4: Based on the proton exchange membrane electrolytic cell model, a separator model is constructed. The anode separator model is constrained by a phase equilibrium equation, and the separation efficiency is solved based on the anode separation temperature, pressure, and the physical property parameters of oxygen and water. Then, based on the physical property parameters of the cooling water and the mixed gas, the energy conservation equation is used for constraint. By inputting the final temperature of the cooling water, the waste heat used by the cooling water heat exchanger model is obtained.

[0042] S5: Construct a deep cold air separation system model, which includes the mathematical constraint model of air compressor, cooling water heat exchanger, air expander, nitrogen separator. By inputting the electric energy given by the photovoltaic power generation system model, the mass flow, temperature and pressure of the produced nitrogen are obtained.

[0043] S6: In order to simulate the process of producing ammonia from nitrogen and hydrogen, construct an ammonia synthesis subsystem model, which adopts Haber-Bosch process to produce ammonia. The ammonia synthesis subsystem model includes the mathematical constraint model of ammonia synthesis reactor, heat pump, ammonia separator, cooling water heat exchanger. By inputting the mass flow, temperature, pressure of hydrogen and nitrogen, and the electric energy given by the photovoltaic power generation system model, the mass flow, temperature, pressure of the final produced ammonia are obtained.

[0044] S7: The ammonia synthesis reactor adopts a three-layer catalytic bed mathematical model, which includes reactor reaction rate constraint equation, reactor structure parameters, reaction kinetics parameters, operating conditions. By inputting the required temperature and pressure of the reaction, as well as the internal reaction property parameters of the reactor (partial pressure of hydrogen and oxygen, and reaction equilibrium constant), the ammonia generation rate in the final model and the temperature and pressure of ammonia at that time are obtained.

[0045] S8: According to the ammonia synthesis reactor model, construct a heat pump model. The heat pump model is constrained by the heat calculation formula, and by inputting the heating heat, the temperature of the heated hydrogen-nitrogen mixture is obtained. The ammonia separator constraint model is based on the separation temperature and pressure, and the separation efficiency is solved based on the property parameters of ammonia. The cooling water heat exchanger model is constrained by the energy conservation equation, and by inputting the final temperature of the hot stream, the waste heat utilized by the cooling water heat exchanger is calculated.

[0046] Solar photovoltaic panel assembly control equation, including electrical efficiency and thermal efficiency.

[0047] Electrical efficiency equation:

[0048] P el =N PV / T η PV / T，e τGA PV / T (1-1)

[0049] Thermal efficiency equation:

[0050] Q th =N PV / T GA PV / T τη PV / T，t (1-η PV / T，e ) (1-2)

[0051] Where τ is the light efficiency of the solar photovoltaic panel assembly, A PV / T is the area of the solar photovoltaic panel assembly (m 2 ), NPV / T is the number of solar photovoltaic panel assemblies, G is the solar radiation value (W / m 2 ), η PV / T，t is the thermal efficiency of the solar photovoltaic panel assembly, η PV / T，e is the electrical efficiency of the solar photovoltaic panel assembly.

[0052] The control equation of the separator simulation model is the phase balance equation; the control equation of the cooling water heat exchanger simulation model is the energy conservation equation.

[0053] The control equation of the proton exchange membrane electrolyzer simulation model includes:

[0054] The mass conservation equation:

[0055]

[0056] i is the actual electrolyzer current density (A / cm 2 ), Z represents the number of transferred electrons, N c represents the number of cells, n F refers to the Faraday efficiency, which can be obtained using the stoichiometric ratio of the chemical reaction, the oxygen generation rate and the water consumption rate, and combined with the subsequent process constraint equation, the hydrogen production amount at different proton exchange membrane electrolyzer temperatures can be calculated.

[0057] The voltage calculation equation:

[0058] V cell = V ocv + V act + V ohm + V con (4-2)

[0059]

[0060] V act is the activation overpotential, which is used to describe the potential required to initiate a reaction at the electrode. It directly represents the speed of the reaction, which is composed of the anode spark overpotential and the cathode activation overpotential:

[0061] V act = V act，a + V act，c (4-3)

[0062]

[0063] wherein i0 is the theoretical electrolyzer current density (A / cm 2 ), and a is the cathode charge transfer coefficient.

[0064] V ohm is the ohmic overvoltage used to simulate the irreversibility caused by the limited conductivity of the cell.

[0065] V ohm =iR eq (4-6)

[0066] where R eq represents the resistance of different elements in all batteries (Ω), usually only including the resistance of the membrane.

[0067] V con is the concentration overpotential, used to simulate the resistance caused by mass transfer inside the battery. The concentration overpotential can be described as a function of electric density and temperature:

[0068]

[0069] where β represents the correction factor, which is 0.2 here, i lim is the maximum electric density, which is 10 A / cm 2 .

[0070] Energy conservation equation:

[0071]

[0072] where h i is the specific enthalpy of substance i (J / kg), N i is the molar flow rate of the corresponding substance into and out of the electrolytic cell (mol / s), C th is the sum of the lumped heat capacity of the components (kW), Q net includes all heat sources and heat losses of the components (kW).

[0073] The electrical efficiency of the electrolytic cell is calculated by the following formula:

[0074]

[0075] where, is the low heating value of H2 (kJ / mol), W net is the power consumption of the electrolytic cell (kW).

[0076] The property calculation of the deep cryogenic air separation molecular system simulation model uses the ideal gas state equation:

[0077]

[0078] where P is the pressure (Pa), T is the temperature (K), V m is the molar volume (m 3 / mol), R is the universal gas constant, a(T) is the attractive parameter, and b is the repulsive parameter.

[0079] The control equation of the compressor and expander simulation model building method uses the energy conservation equation.

[0080] The method for establishing the simulation model of the ammonia synthesis reactor adopts a three-layer catalytic bed mathematical model, and the reaction rate control equation includes:

[0081]

[0082] wherein r is the reaction rate (mol NH3 / h / m 3 ), K2 is the reverse reaction rate constant (mol / (L·s)), are the fugacities of nitrogen, hydrogen and ammonia (atm), K a is the equilibrium constant of the reaction.

[0083] The control equation of the heat pump simulation model adopts the energy conservation equation under the thermodynamic cycle efficiency. DETAILED EMBODIMENT

[0085] As Figure 1 . Firstly, the PV / T assembly absorbs solar energy to convert into electric energy. In the water electrolysis hydrogen production subsystem, the electric energy drives the proton exchange membrane electrolyzer to produce hydrogen, and the waste heat of the proton exchange membrane electrolyzer is utilized through the heat exchanger-1; the hydrogen is transported after separation, purification and compression. On the other side, in the deep cooling air separation subsystem, the air compressor and the expander work cooperatively to obtain ultra-low temperature air, and then the nitrogen is separated out; the waste heat of the compressed air is utilized through the heat exchanger-2. The pure hydrogen and nitrogen are mixed into hydrogen-nitrogen mixed gas in proportion, and after preheating through the heat exchanger-3 and temperature rising through the heater, the hydrogen-nitrogen mixed gas enters the three-layer catalytic bed reactor to carry out the ammonia synthesis reaction; the high-temperature ammonia-containing gas generated by the reaction recovers heat through the heat exchanger-4 (for preheating the raw material gas), and then the liquid ammonia product is obtained after cooling and separation. The unreacted hydrogen-nitrogen mixed gas is recycled and compressed to re-enter the synthesis process, so as to realize efficient utilization of raw materials.

[0086] The model parameters involved in the embodiment are given in the specific calculation process.

[0087] (1) The model of the solar photovoltaic power generation panel assembly is constructed, the solar radiation value is set to 514 W / m 2 , the solar photovoltaic power generation panel assembly light efficiency τ is 0.855, the number of solar photovoltaic power generation panel assemblies N PV / T is 1200, and the area A PV / T of the assembly is 2.7 m 2 .

[0088] (2) The proton exchange membrane electrolyzer in the water electrolysis hydrogen production subsystem model is constructed, the cell temperature is set to 80℃, the cathode pressure is set to 16 bar, the anode pressure is set to 8 bar, the number of transferred electrons Z is set to 2, and the number of cells N cThe power consumption is 1200, and the power consumption is 228 kW. The inlet water mass flow rate is 17970 kg / hr, the temperature is 80℃, and the pressure is 8 bar.

[0089] (3) The anode separator model in the electrolytic water hydrogen production subsystem model is constructed, and the separation temperature is set to 80℃ and the pressure is set to 8 bar. The cathode separator model is set to a separation temperature of 80℃ and a pressure of 8 bar. The cooling water heat exchanger model is set to an outlet temperature difference of 1k between the hot and cold streams.

[0090] (4) The cryogenic air separation subsystem is constructed, and the air compressor consumes photovoltaic panel assembly power of 32Kw, the discharge pressure is 200bar, the expander discharge pressure is 1bar, the nitrogen separator separation temperature is -193℃, and the pressure is 1bar.

[0091] (5) The three-layer catalytic bed reactor model in the ammonia synthesis subsystem model is constructed, and the three-layer catalytic bed specific reaction temperature settings are 485℃, 452℃, and 425℃, respectively, and the operating pressure is 193bar. The three-layer catalytic bed is made of Inconel 600, and contains 2cm 3 of 0.42-0.55mm size catalysts. The mole fraction of ammonia gas at the inlet of the catalytic bed should be between 6%-13%.

[0092] (6) The heat pump model in the ammonia synthesis subsystem model is constructed. The heat pump is set to a heating capacity of 23kW, the ammonia separator model is set to a separation temperature of -25℃ and a pressure of 193bar, and a separation temperature of -27℃ and a pressure of 18bar. The cooling water heat exchanger is set to an outlet temperature of 235℃.

[0093] Under the above steps, the constructed subsystem models are connected according to the process flow, and the solar photovoltaic panel assembly model generates 273.78kW of electricity under the condition of radiation intensity of 514W / m 2 , of which 83.4% is supplied to the electrolytic water hydrogen production subsystem, and finally 4.07kg / hr of H2 is obtained. 4.82% of the electricity generated by the solar photovoltaic panel assembly model is used for the air compressor of the cryogenic air separation subsystem model, and 11.99kW of heat energy is recovered in the subsystem. The remaining 11.78% of the electricity generated by the solar photovoltaic panel assembly model is used by the ammonia synthesis subsystem model, which additionally requires 23kW of external heat energy as auxiliary, and 22.4kg / hr of ammonia and 24kW of recovered heat value are obtained. If the efficiency of each subsystem and the amount of ammonia produced are used as indicators, different operating conditions are controlled for analysis, and the changes in the mass flow rates of ammonia and hydrogen under different tank temperatures and input power changes are shown in Figure 2 As can be seen from the figure, under different tank temperatures, as the input power increases, the mass flow rates of ammonia and hydrogen increase linearly, and the growth is not sensitive to changes in tank temperature.

[0094] Figure 3 The ammonia molar fraction of Bed 3 continues to increase with temperature rising and reaches the peak at 425℃, then decreases. The change of Bed 2 is gentle, and the temperature adaptability is relatively strong, reaching the peak at 452℃. Bed 1 reaches the peak at 485℃, and the ammonia concentration in the high temperature zone drops sharply. This shows that the ammonia generation-decomposition balance of each catalyst bed responds differently to temperature. Bed 3 is more sensitive to temperature and is suitable for the medium temperature zone. Bed 1 is prone to ammonia decomposition at high temperature, so high temperature conditions need to be controlled.

Claims

1. A system modeling method for hydrogen production via proton exchange membrane electrolysis and ammonia synthesis via cryogenic air separation, characterized by: Specifically, this includes methods for establishing solar photovoltaic power generation systems, electrolytic water hydrogen production subsystems, cryogenic air molecular systems, and ammonia synthesis subsystems. The steps for model construction are as follows: S1: Establishment of a solar photovoltaic power generation system: It is beneficial for solar photovoltaic power generation panels to input solar radiation values ​​to obtain photovoltaic power. The control equations of the solar photovoltaic power generation panels include electrical efficiency and thermal efficiency. S2: Construct a subsystem model for hydrogen production by water electrolysis, which includes mathematical constraint models for a proton exchange membrane electrolyzer, a cooling water heat exchanger, an anode separator, and a cathode separator. By inputting the electrical energy from the photovoltaic power generation system model, the mass flow rate, temperature, and pressure of the produced hydrogen are obtained. S3: The mathematical constraint model of the proton exchange membrane electrolyzer includes mass conservation, voltage calculation and energy conservation equations. In the mathematical model of the proton exchange membrane electrolyzer, the electrical energy given by the photovoltaic power generation system model is input to obtain the mass flow rate, temperature and pressure of the proton exchange membrane electrolyzer for producing hydrogen by electrolysis of water. S4: Based on the proton exchange membrane electrolyzer model, a separator model is constructed. The anode separator model is constrained by the phase equilibrium equation. The separation efficiency is solved based on the anode separation temperature, pressure, and the physical properties of oxygen and water. Then, based on the physical properties of cooling water and mixed gas, the energy conservation equation is used to constrain the model. By inputting the final temperature reached by the cooling water, the waste heat utilized by the cooling water heat exchanger model is obtained. S5: Construct a cryogenic air molecular system model, which includes mathematical constraint models of an air compressor, a cooling water heat exchanger, an air expander, and a nitrogen separator. By inputting the electrical energy given by the photovoltaic power generation system model, the mass flow rate, temperature, and pressure of nitrogen production are obtained. S6: To simulate the process of producing ammonia from nitrogen and hydrogen, a synthetic ammonia subsystem model is constructed. The Haber-Bosch process is used to produce ammonia. The synthetic ammonia subsystem model includes mathematical constraint models of the synthetic ammonia reactor, heat pump, ammonia separator, and heat exchanger. By inputting the mass flow rate, temperature, and pressure of hydrogen and nitrogen, and the electrical energy given by the photovoltaic power generation system model, the mass flow rate, temperature, and pressure of the final produced ammonia are obtained. S7: The ammonia synthesis reactor adopts a three-layer catalytic bed mathematical model, including the reactor reaction rate constraint equation, reactor structural parameters, reaction kinetic parameters, and operating conditions. By inputting the temperature, pressure, and physical property parameters of the reaction inside the reactor, including the partial pressure of hydrogen and oxygen and the reaction equilibrium constant, the ammonia generation rate and the temperature and pressure of ammonia at this time in the final model are obtained. S8: Based on the ammonia synthesis reactor model, a heat pump model is constructed. The heat pump model is constrained by the heat calculation formula. By inputting the heating heat energy, the temperature of the hydrogen-nitrogen mixture after heating is obtained. The ammonia separator constrained model is calculated based on the separation temperature and pressure, and the physical properties of ammonia. The cooling water heat exchanger model is constrained by the energy conservation equation. By inputting the final temperature reached by the heat flow stream, the waste heat utilized by the cooling water heat exchanger is calculated.

2. The system modeling method for proton exchange membrane electrolysis of water to produce hydrogen and cryogenic air separation to synthesize ammonia according to claim 1, characterized in that: The control equations for the solar photovoltaic panel module include electrical efficiency and thermal efficiency. Electrical efficiency equation: P el =N PV / T or PV / T,e τGA PV / T (2-1) Thermal efficiency equation: Q th =N PV / T GA PV / T the PV / T,t (1st) PV / T,e ) (2-2) Where τ is the light efficiency of the solar photovoltaic panel module, and A PV / T N is the area of ​​the solar photovoltaic panel module. PV / T G is the number of solar photovoltaic panels, η is the solar radiation value, and G is the number of solar photovoltaic panels. PV / T，t It is the thermal efficiency of solar photovoltaic panels, η PV / T，e It refers to the electrical efficiency of solar photovoltaic panels.

3. The system modeling method for proton exchange membrane electrolysis of water to produce hydrogen and cryogenic air separation to synthesize ammonia according to claim 1, characterized in that: The control equations of the separator simulation model are phase equilibrium equations; the control equations of the heat exchanger simulation model are energy conservation equations.

4. The system modeling method for proton exchange membrane electrolysis of water to produce hydrogen and cryogenic air separation to synthesize ammonia according to claim 1, characterized in that: The governing equations of the proton exchange membrane electrolyzer simulation model include: mass conservation equation: i is the actual electrolytic cell voltage, Z represents the number of transferred electrons, and N... c n represents the number of batteries. F The Faraday efficiency, derived from stoichiometry of chemical reactions, measures the rate of oxygen production and water consumption. Combined with subsequent process constraint equations, it allows for calculations to determine the hydrogen production rate at different proton exchange membrane electrolyzer temperatures. Voltage calculation equation: V cell =V ocv +V act +V ohm +V con (4-2) Among them, V ocv This refers to the open-circuit voltage, V act It is the activation overpotential, used to describe the potential required to initiate a reaction at the electrode, V. ohm It is an ohmic overvoltage, used to simulate the irreversibility caused by the finite conductivity of a battery, V con It is the concentration overpotential, used to simulate the resistance caused by mass transfer inside the battery. Energy conservation equation: Among them, h i It is the specific enthalpy of substance i, N i C is the molar flow rate of the corresponding substance entering and exiting the electrolytic cell. th It is the sum of the lumped heat capacities of the components, Q net It includes all heat sources and heat losses of the components. The electrical efficiency of an electrolytic cell is calculated using the following formula: in, It is the lower heating value of H2, W net It is the power consumed by the electrolytic cell.

5. The system modeling method for proton exchange membrane electrolysis of water to produce hydrogen and cryogenic air separation to synthesize ammonia according to claim 1, characterized in that: The physical property calculations of the cryogenic air molecule system simulation model are performed using the ideal gas law.

6. The system modeling method for proton exchange membrane electrolysis of water to produce hydrogen and cryogenic air separation to synthesize ammonia according to claim 1, characterized in that: The control equations for the compressor and expander simulation models adopt the energy conservation equation.

7. The system modeling method for proton exchange membrane electrolysis of water to produce hydrogen and cryogenic air separation to synthesize ammonia according to claim 1, characterized in that: The control equations for the ammonia synthesis reactor simulation model are based on the reaction rate control equations.

8. The system modeling method for proton exchange membrane electrolysis of water to produce hydrogen and cryogenic air separation to synthesize ammonia according to claim 1, characterized in that: The control equations of the heat pump simulation model adopt the energy conservation equation under thermodynamic cycle efficiency.

Images