PEM water electrolysis hydrogen production system and control method thereof

Abstract

The invention discloses a PEM water electrolysis hydrogen production system and a control method thereof.The control method mainly comprises the steps that an electrolytic bath temperature model, an electrolytic bath runner model, a first-stage steam-water separator model and a second-stage steam-water separator model are mainly used for establishing the dynamic relation of the current of an electrolytic bath, the cathode outlet pressure and the outlet temperature of a second-stage steam-water separator; meanwhile, the cooling liquid flow of the second-stage steam-water separator is controlled based on PID, so that the outlet temperature of the second-stage steam-water separator meets the gas inlet condition of the hydrogen purification device, and the gas inlet valve is controlled to be opened and closed according to the outlet temperature of the second-stage steam-water separator so as to ensure that the temperature of gas entering the purification system is stabilized in a suitable range; the starting condition of the front air inlet valve of the purification device is met. Therefore, potential damage to the purification system caused by abnormal temperature is effectively avoided, safe and efficient operation of the whole system is guaranteed, the gas purification efficiency is optimized, and efficient operation of the purification device is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of water electrolysis hydrogen production, and in particular to a PEM water electrolysis hydrogen production system and a control method thereof. Background Art

[0002] The PEM water electrolysis hydrogen production system includes a pre-purification system, which includes a primary steam-water separator and a secondary steam-water separator.

[0003] The primary steam-water separator achieves effective removal of water from steam by slowing down the flow rate, using centrifugal force and baffle collisions to cause droplets to condense and separate by gravity. The specific principle is that when steam containing droplets enters the separator, its speed is first slowed down due to space limitations, and then moves in a curved path. The droplets are deviated from the steam flow by inertia and centrifugal force and hit the baffle or the wall. This process not only increases the chance of droplet collision, but also causes them to change the direction of movement and disperse upward or outward. At the same time, due to the reduction in speed and multiple collisions, droplets condense to form larger droplets. These large droplets are affected by gravity, gather at the bottom of the separator and are discharged, while the purified steam continues to flow along the pipeline. The whole process embodies key steps such as speed reduction, centrifugal separation, collision and deflection, condensation and collection, which effectively improves the efficiency of steam-water separation.

[0004] The secondary steam-water separator uses the thermal conductivity of aluminum to exchange heat between water and hydrogen, lowering the outlet temperature of the secondary steam-water separator to a suitable temperature and further separating the water in the gas by reducing the saturated vapor pressure. The principle is to reduce the hydrogen temperature through convection heat transfer technology, thereby effectively reducing the saturated vapor pressure of water in the gas and causing the water vapor to condense into liquid water droplets. At the same time, through physical structures such as tortuous channels or specific fluid guides, the collision and aggregation of water droplets in the airflow are enhanced, further improving the separation efficiency of water droplets and dry hydrogen, ensuring the high purity and low humidity characteristics of the final hydrogen product.

[0005] In summary, the pre-purification system is a key factor in ensuring the long-life operation of the purification system. How to keep the outlet temperature of the secondary steam-water separator within a stable range is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In view of the above-mentioned deficiencies, the technical problem to be solved by the present invention is: to provide a PEM water electrolysis hydrogen production system and a control method thereof, so as to stabilize the outlet temperature of the purification system within the operating temperature range, effectively avoid the potential damage to the purification system caused by temperature abnormalities, ensure the overall safety and efficient operation of the system, optimize the gas purification efficiency, and thus achieve efficient operation of the purification device.

[0007] In order to solve the above technical problems, the technical solution of the present invention is:

[0008] A control method for a PEM water electrolysis hydrogen production system, the hydrogen production system comprising an electrolyzer, a pre-purification system and a purification system, the pre-purification system comprising a primary steam-water separator and a secondary steam-water separator, an air intake valve being arranged between the air outlet of the secondary steam-water separator and the air inlet of the purification system; the control method comprising the following steps:

[0009] Step 1, obtaining the current, voltage and cathode outlet pressure of the electrolytic cell;

[0010] Step 2: inputting current, voltage and cathode outlet pressure into a preset mathematical model to establish a dynamic relationship between the electrolytic cell current, cathode outlet pressure and secondary steam-water separator outlet temperature T2;

[0011] Step 3: Establish the coolant flow rate q of the secondary steam-water separator cl and coolant temperature T cl The relationship is: Q cl =C cl ×T cl ×q cl , Q in the formula cl is the heat dissipation of the coolant, C cl is the specific heat capacity of the coolant, T cl is the secondary separator coolant temperature, q cl is the coolant flow rate of the secondary water separator;

[0012] Step 4: Based on the above relationship, proportional calculus PID is used to control the coolant flow rate q of the secondary steam-water separator cl , so that the outlet temperature T2 of the secondary steam-water separator is stable within the range required by the purification system.

[0013] Preferably, the control method further comprises the following steps:

[0014] Determine whether the outlet temperature T2 of the secondary steam-water separator is greater than T ch , T ch is the desired temperature at the inlet of the purification system;

[0015] If the outlet temperature T2 of the secondary steam-water separator is not greater than T ch , open the intake valve;

[0016] If the secondary steam-water separator outlet temperature T2 is greater than T ch , close the intake valve.

[0017] Preferably, the mathematical model includes an electrolytic cell temperature model, an electrolytic cell flow channel model, a primary steam-water separator model, and a secondary steam-water separator model; then the step 2 includes:

[0018] Input current, voltage and cathode outlet pressure to the electrolytic cell temperature model and electrolytic cell flow channel model;

[0019] The electrolytic cell temperature model calculates the internal temperature of the electrolytic cell;

[0020] The electrolyzer flow channel model calculates the hydrogen mole fraction and water mole fraction at the electrolyzer outlet;

[0021] Input the internal temperature of the electrolyzer, the hydrogen mole fraction, and the water mole fraction to the primary steam-water separator model;

[0022] The first-stage steam-water separator model calculates the outlet temperature and outlet pressure of the first-stage steam-water separator;

[0023] Input the outlet temperature and outlet pressure of the first-stage steam-water separator into the second-stage steam-water separator model;

[0024] The secondary steam-water separator model calculates the secondary steam-water separator outlet temperature T2 to establish a dynamic relationship between the electrolytic cell current, cathode outlet pressure and the secondary steam-water separator outlet temperature T2.

[0025] A preferred method is to pre-set the electrolytic cell temperature model, comprising the following steps:

[0026] First calculate the coolant flow Q el , Q el =(U el -V th )In cell ;

[0027] Then calculate the internal temperature T of the electrolytic cell stack ,

[0028]

[0029] In the formula: U el is the electrolyzer input voltage, V th is the theoretical voltage of a single cell in the electrolytic cell, I is the input current of the electrolytic cell, and n cell is the number of single chambers in the electrolytic cell, T stack is the internal temperature of the electrolytic cell, C stack is the specific heat capacity of the electrolytic cell, q cl0 is the coolant flow in the thermal management water circuit, C cl is the specific heat capacity of the coolant, T stack is the electrolytic cell temperature, T in，PEM is the coolant inlet temperature, Q gas is the heat dissipation.

[0030] A preferred method is to pre-set the electrolytic cell flow channel model, comprising the following steps:

[0031] According to the mass conservation equation, the changes of hydrogen and water components and water in the electrolyzer flow channel are analyzed;

[0032] The amount of hydrogen flow rate is equal to the amount of hydrogen at the outlet minus the amount of hydrogen generated;

[0033] The hydrogen and water in the cathode are calculated using the following formula:

[0034]

[0035] In the formula: is the number of moles of hydrogen inside the flow channel, is the number of moles of hydrogen at the inlet, is the number of moles of hydrogen at the outlet, is the number of moles of hydrogen produced by the reaction, is the number of moles of water inside the channel, is the number of moles of water at the inlet, is the number of moles of water at the outlet, is the number of moles of water dragged by the electrons, is the number of moles of diffused water;

[0036] The partial pressures of hydrogen and water are calculated according to the ideal gas law, and the cathode pressure is equal to the sum of the partial pressures of hydrogen and water;

[0037]

[0038] In the formula: is the hydrogen partial pressure, is the number of moles of hydrogen, R is the gas constant, T el is the electrolytic cell temperature, V ca is the volume of the electrolytic cell flow channel, is the water partial pressure, is the number of moles of water at the outlet, P ca is the cathode pressure, is the cathode channel hydrogen partial pressure, is the cathode channel water partial pressure;

[0039] Mole fraction of hydrogen:

[0040] Mole fraction of water:

[0041] The amount of hydrogen produced by the chemical reaction can be calculated in real time based on Faraday’s law;

[0042] In the formula, n is the number of single chambers, I is the input current of the electrolytic cell, and F is the Faraday constant.

[0043] A preferred method is to pre-set the primary steam-water separator model, comprising the following steps:

[0044] According to the law of conservation of mass and energy, the temperature and pressure changes caused by the phase change of water inside the first-stage separator are analyzed. According to the law of conservation of mass and the physical structural parameters of the steam-water separator itself, the inlet and water outlet flow equations are established to calculate the gas outlet flow;

[0045] According to the inference of Bernoulli's equation, the internal pressure drop of the first-stage steam-water separator is proportional to the square of the volume flow rate, and the inlet flow equation can be obtained as shown in formula (1):

[0046]

[0047] In the formula: m in is the separator inlet flow mass, p in is the separator inlet pressure, T in is the separator inlet temperature, p out，gas is the gas outlet pressure of the steam-water separator, Q in，ref is the reference volume flow rate of the water separator, Δp sep，ref is the reference pressure drop of the water separator, M mix is the average molar mass of the mixed gas in the steam-water separator;

[0048] According to the inference of Bernoulli equation, the water outlet flow equation can be obtained as shown in formula (2):

[0049]

[0050] In the formula: m outwater is the water outlet mass flow rate of the steam-water separator, S out，water is the cross-sectional area of ​​the water outlet of the steam-water separator, g is the acceleration due to gravity, L sep is the water level in the steam-water separator;

[0051] According to the law of conservation of mass and the ideal gas equation, the relationship equation between the inlet and outlet flow rates of the steam-water separator is established as shown in formula (3):

[0052]

[0053] In the formula: V sep is the internal volume of the steam-water separator, T out，gas is the gas outlet temperature of the steam-water separator,

[0054] And T out，gas It is T2, m vap，sep is the water vapor liquefaction flow rate of the steam-water separator, R is the gas constant,

[0055] M mix is the average molar mass of the mixed gas in the steam-water separator, p out，gasis the gas outlet pressure of the steam-water separator;

[0056] According to the law of conservation of energy, the calculation equation for the change of enthalpy in the steam-water separator is established to calculate the outlet temperature of the steam-water separator, as shown in formula (4):

[0057]

[0058] In the formula: c V_mix is the constant volume specific heat capacity of the mixed gas inside the steam-water separator, m sep is the mass flow rate of the mixed gas at the outlet of the steam-water separator, T sep is the outlet temperature of the steam-water separator, H in is the enthalpy flow rate at the steam-water separator inlet, H LHV is the latent heat of vaporization,

[0059] H out，vap is the enthalpy of the outlet hydrogen, H out，gas is the enthalpy of outlet water vapor;

[0060] Calculate the enthalpy flow rate H of the inlet and outlet fluid mix As shown in formula (5):

[0061] H mix =T∑(m i c p_i ) (5);

[0062] The calculation of latent heat of vaporization is shown in formula (6):

[0063]

[0064] When the outlet temperature T out，gas Finally, the saturated vapor pressure is calculated according to the saturated vapor pressure fitting equation, and the mass of condensed water and the gas outlet pressure are calculated;

[0065] The saturated vapor pressure fitting equation is shown in formula (7):

[0066]

[0067] The condensed water mass is calculated as shown in formula (8):

[0068]

[0069] The calculation of gas outlet pressure is shown in formula (9):

[0070]

[0071] Due to the generation of liquid water, the volume of gas that can be accommodated in the steam-water separator will change. The calculation of the volume of the steam-water separator is shown in formula (10):

[0072]

[0073] In the formula: V sep，0 is the initial volume of the separator, V sep is the volume of the water separator, m vap，sep is the quality of condensed water.

[0074] A preferred method is to pre-set the secondary steam-water separator model, comprising the following steps:

[0075] Secondary steam-water separator outlet temperature T sep2，out The calculation formulas for are shown in formula (12) and formula (13):

[0076] Q cl =A×K×(T sep2 -T cl ) (12);

[0077] Q in the formula cl is the heat dissipation of the coolant, T cl is the coolant temperature, A is the heat transfer area, K is the heat transfer coefficient, T sep2 is the internal temperature of the secondary steam-water separator;

[0078]

[0079] In the formula, T sep2，in is the gas temperature at the inlet of the secondary separator, T sep2，out is the outlet gas temperature of the secondary steam-water separator.

[0080] A PEM water electrolysis hydrogen production system, comprising an electrolyzer, a pre-purification system and a purification system, wherein the pre-purification system comprises a primary steam-water separator and a secondary steam-water separator, an air intake valve is arranged between the air outlet of the secondary steam-water separator and the air intake of the purification system, the hydrogen production system further comprises a control unit and a parameter input unit, a dynamic relationship establishment unit and a PID closed-loop control unit electrically connected to the control unit respectively, and the control unit is also electrically connected to the air intake valve;

[0081] The parameter input unit is used to obtain the current, voltage and cathode outlet pressure of the electrolytic cell, and transmit the current, voltage and cathode outlet pressure of the electrolytic cell to the dynamic relationship establishment unit;

[0082] The dynamic relationship establishing unit is used to input the current, voltage and cathode outlet pressure into a preset mathematical model, and the mathematical model establishes the dynamic relationship between the current of the electrolyzer, the cathode outlet pressure and the outlet temperature of the secondary steam-water separator, and the mathematical model calculates and transmits the coolant flow rate q cl and coolant temperature T clTo the PID closed-loop control unit;

[0083] The PID closed-loop control unit is used to receive the coolant flow rate q cl and coolant temperature T cl , proportional calculus PID is used to control the coolant flow q of the secondary steam-water separator cl , so that the outlet temperature of the secondary steam-water separator is stable within the range required by the purification system.

[0084] A preferred embodiment is that the hydrogen production system also includes an air intake control unit, which is electrically connected to the control unit; the air intake control unit is used to determine whether the outlet temperature T2 of the secondary steam-water separator is greater than the required temperature of the purification system inlet, and if the outlet temperature T2 of the secondary steam-water separator is not greater than the required temperature of the purification system inlet, a corresponding opening signal is generated; if the outlet temperature T2 of the secondary steam-water separator is greater than the required temperature of the purification system inlet, a corresponding closing signal is generated; finally, the air intake control unit transmits an opening signal or a closing signal to the control unit; the control unit controls the air intake valve to open according to the received opening signal, and controls the air intake valve to close according to the received closing signal.

[0085] Preferably, the hydrogen production system further comprises a presetting unit, and the presetting unit is used to pre-set the mathematical model.

[0086] After adopting the above technical solution, the beneficial effects of the present invention are:

[0087] Since the PEM water electrolysis hydrogen production system and its control method of the present invention mainly utilize the electrolyzer temperature model, electrolyzer flow channel model, primary steam-water separator model and secondary steam-water separator model to establish the dynamic relationship between the electrolyzer current, cathode outlet pressure and secondary steam-water separator outlet temperature T2, and at the same time control the coolant flow of the secondary steam-water separator based on PID, so that the secondary steam-water separator outlet temperature meets the air intake conditions of the hydrogen purification device, so as to ensure that the gas temperature entering the purification system is stable within an appropriate range and meets the conditions for starting the front-end valve of the purification device. It can be seen that the present invention effectively avoids the potential damage to the purification system caused by abnormal temperature, ensures the overall safety and efficient operation of the system, optimizes the gas purification efficiency, and thus realizes the efficient operation of the purification device. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 It is a flow chart of a control method of a PEM water electrolysis hydrogen production system in the present invention;

[0089] Figure 2 It is a schematic diagram of the PEM water electrolysis hydrogen production system of the present invention;

[0090] Figure 3It is a principle block diagram of the PEM water electrolysis hydrogen production system in the present invention;

[0091] In the figure: 1-electrolyzer, 2-primary steam-water separator, 3-secondary steam-water separator, 4-pressure sensor, 5-intake valve, 100-pre-purification system, 200-purification system. DETAILED DESCRIPTION

[0092] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0093] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0094] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0095] Embodiment 1:

[0096] like Figure 1 As shown, a control method of a PEM water electrolysis hydrogen production system is applied to the PEM water electrolysis hydrogen production system described in Example 2. The control method of the present invention comprises the following steps:

[0097] Step 1, obtaining the current, voltage and cathode outlet pressure of the electrolytic cell;

[0098] It should be noted that the current and voltage of the electrolytic cell can be input by the human-computer interaction unit, and the cathode outlet pressure can be measured by the pressure sensor located at the cathode outlet of the electrolytic cell ( Figure 2 Figure 8 shows the pressure sensor (P) collecting data. Figure 2 In the figure, I is the current and U is the voltage.

[0099] Step 2: inputting current, voltage and cathode outlet pressure into a preset mathematical model to establish a dynamic relationship between the electrolytic cell current, cathode outlet pressure and secondary steam-water separator outlet temperature T2;

[0100] In this embodiment, the mathematical model includes an electrolytic cell temperature model, an electrolytic cell flow channel model, a primary steam-water separator model, and a secondary steam-water separator model; this step is specifically as follows:

[0101] Input current, voltage and cathode outlet pressure to the electrolytic cell temperature model and electrolytic cell flow channel model;

[0102] The electrolytic cell temperature model calculates the internal temperature of the electrolytic cell;

[0103] The electrolyzer flow channel model calculates the hydrogen mole fraction and water mole fraction at the electrolyzer outlet;

[0104] Input the internal temperature of the electrolyzer, the hydrogen mole fraction, and the water mole fraction to the primary steam-water separator model;

[0105] The first-stage steam-water separator model calculates the outlet temperature and outlet pressure of the first-stage steam-water separator;

[0106] Input the outlet temperature and outlet pressure of the first-stage steam-water separator into the second-stage steam-water separator model;

[0107] The secondary steam-water separator model calculates the secondary steam-water separator outlet temperature T2 to establish a dynamic relationship between the electrolytic cell current, cathode outlet pressure and the secondary steam-water separator outlet temperature T2.

[0108] Step 3: Establish the coolant flow rate q of the secondary steam-water separator cl and coolant temperature T cl The relationship is: Q cl =C cl ×T cl ×q cl , Q in the formula cl is the heat dissipation of the coolant, C cl is the specific heat capacity of the coolant, T cl is the secondary separator coolant temperature, q cl is the coolant flow rate of the secondary steam-water separator;

[0109] It should be noted that the coolant flow rate q cl and coolant temperature T cl It is calculated by mathematical model.

[0110] Step 4: Use proportional calculus PID to control the coolant flow q of the secondary steam-water separator cl , so that the outlet temperature T2 of the secondary steam-water separator is stable within the range required by the purification system.

[0111] The control method in this embodiment further includes the following steps:

[0112] Determine whether the outlet temperature T2 of the secondary steam-water separator is greater than T ch , T ch is the desired temperature at the inlet of the purification system;

[0113] If the outlet temperature T2 of the secondary steam-water separator is not greater than T ch , that is, T2≤T ch When the air intake valve is opened;

[0114] If the secondary steam-water separator outlet temperature T2 is greater than T ch , that is, T2>T ch When the air inlet valve is closed.

[0115] like Figure 1 As shown, the control method of the PEM water electrolysis hydrogen production system of the present invention mainly utilizes the electrolyzer temperature model, the electrolyzer flow channel model, the primary water separator model and the secondary water separator model to establish the dynamic relationship between the electrolyzer current, the cathode outlet pressure and the secondary water separator outlet temperature T2, and at the same time controls the coolant flow of the secondary water separator based on PID, so that the secondary water separator outlet temperature meets the intake conditions of the hydrogen purification device, and then controls the opening and closing of the intake valve according to the secondary water separator outlet temperature, so as to ensure that the gas temperature entering the purification system is stable within an appropriate range and meets the conditions for starting the front valve of the purification device. It can be seen that the control method of the present invention effectively avoids the potential damage to the purification system caused by abnormal temperature, ensures the overall safety and efficient operation of the system, optimizes the gas purification efficiency, and thus realizes the efficient operation of the purification device.

[0116] The electrolytic cell temperature model in the present invention is used to calculate the internal temperature T of the electrolytic cell. stack , then the electrolytic cell temperature model is preset, specifically including the following steps:

[0117] First calculate the electrolytic cell coolant flow Q el , Q el =(U el -V th )In cell ;

[0118] Then calculate the internal temperature T of the electrolytic cell stack ,

[0119]

[0120] In the formula: U el is the electrolyzer input voltage, V th is the theoretical voltage of a single cell in the electrolytic cell, I is the input current of the electrolytic cell, and n cell is the number of single chambers in the electrolytic cell, T stack is the internal temperature of the electrolytic cell, Cstack is the specific heat capacity of the electrolytic cell, q cl0 is the coolant flow in the thermal management water circuit, C cl is the specific heat capacity of the coolant, T stack is the electrolytic cell temperature, T in，PEM is the coolant inlet temperature, Q gas is the heat dissipation.

[0121] The electrolyzer flow channel model of the present invention is used to calculate the hydrogen mole fraction at its outlet and water mole fraction Then, the electrolytic cell flow channel model is preset, which specifically includes the following steps:

[0122] According to the mass conservation equation, the changes in hydrogen and water components (molar fraction) and water in the electrolyzer flow channel are analyzed;

[0123] The cathode is where hydrogen is formed, and the half-reaction equation is:

[0124] 4H + +4e - →H 2 ;

[0125] The amount of hydrogen flow rate is equal to the amount of hydrogen at the outlet minus the amount of hydrogen generated;

[0126] Hydrogen and water are calculated using the following formula:

[0127]

[0128] In the formula: is the number of moles of hydrogen inside the flow channel, is the number of moles of hydrogen at the inlet, is the number of moles of hydrogen at the outlet, is the number of moles of hydrogen produced by the reaction, is the number of moles of water inside the channel, is the number of moles of water at the inlet, is the number of moles of water at the outlet, is the number of moles of water dragged by the electrons, is the number of moles of diffused water;

[0129] The partial pressures of hydrogen and water are calculated according to the ideal gas law, and the cathode pressure is equal to the sum of the partial pressures of hydrogen and water;

[0130]

[0131] In the formula: is the hydrogen partial pressure, is the number of moles of hydrogen, R is the gas constant, T el is the electrolytic cell temperature, V ca is the volume of the electrolytic cell flow channel, is the water partial pressure, is the number of moles of water at the outlet, P ca is the cathode pressure, is the cathode channel hydrogen partial pressure, is the cathode channel water partial pressure;

[0132] Mole fraction of hydrogen:

[0133]

[0134] Mole fraction of water:

[0135]

[0136] The amount of hydrogen produced by the chemical reaction can be calculated in real time based on Faraday’s law;

[0137] In the formula, n is the number of single chambers, I is the input current of the electrolytic cell, and F is the Faraday constant. The first-stage steam-water separator model in the present invention is used to calculate its outlet temperature and outlet pressure pout,gas, and the first-stage steam-water separator model is pre-set, specifically including the following steps:

[0138] According to the law of conservation of mass and energy, the temperature and pressure changes caused by the phase change of water inside the first-stage separator are analyzed. According to the law of conservation of mass and the physical structural parameters of the steam-water separator itself, the inlet and water outlet flow equations are established to calculate the gas outlet flow;

[0139] According to the inference of Bernoulli's equation, the internal pressure drop of the first-stage steam-water separator is proportional to the square of the volume flow rate, and the inlet flow equation can be obtained as shown in formula (1):

[0140]

[0141] In the formula: m in is the mass flow rate at the steam-water separator inlet, in kg s -1 ;

[0142] p in is the inlet pressure of the steam-water separator, in Pa;

[0143] T in is the steam-water separator inlet temperature, in Pa;

[0144] p out，gas is the gas outlet pressure of the steam-water separator, in Pa;

[0145] Q in，ref is the reference volume flow rate of the water separator, in min L -1 ;

[0146] Δp sep，ref is the reference pressure drop of the steam-water separator, in Pa;

[0147] M mix is the average molar mass of the mixed gas in the steam-water separator, in units of min L -1 .

[0148] According to the inference of Bernoulli equation, the water outlet flow equation can be obtained as shown in formula (2):

[0149]

[0150] In the formula: m outwater is the water outlet mass flow rate of the steam-water separator,

[0151] S out，water is the cross-sectional area of ​​the water outlet of the steam-water separator,

[0152] g is the acceleration due to gravity,

[0153] L sep It is the water level in the water separator.

[0154] According to the law of conservation of mass and the ideal gas equation, the relationship equation between the inlet and outlet flow rates of the steam-water separator is established as shown in formula (3):

[0155]

[0156] In the formula: V sep is the internal volume of the steam-water separator, T out，gas is the gas outlet temperature of the steam-water separator,

[0157] And T out，gas It is T2, m vap，sep is the water vapor liquefaction flow rate of the steam-water separator, R is the gas constant,

[0158] M mix is the average molar mass of the mixed gas in the steam-water separator, p out，gas is the gas outlet pressure of the steam-water separator;

[0159] According to the law of conservation of energy, the calculation equation for the change of enthalpy in the steam-water separator is established to calculate the outlet temperature of the steam-water separator, as shown in formula (4):

[0160]

[0161] In the formula: c V_mix is the constant volume specific heat capacity of the mixed gas inside the steam-water separator,

[0162] m sep is the mass flow rate of mixed gas at the outlet of the steam-water separator,

[0163] T sep is the outlet temperature of the steam-water separator,

[0164] H in is the separator inlet enthalpy flow rate,

[0165] H LHV is the latent heat of vaporization,

[0166] H out，vap is the enthalpy of outlet hydrogen,

[0167] H out，gas is the enthalpy of outlet water vapor;

[0168] Calculate the enthalpy flow rate H of the inlet and outlet fluid mix As shown in formula (5):

[0169] H mix =T∑(m i c p_i );

[0170] The calculation of latent heat of vaporization is shown in formula (6):

[0171]

[0172] When the outlet temperature T is obtained out，gas Finally, the saturated vapor pressure is calculated according to the saturated vapor pressure fitting equation, and the mass of condensed water and the gas outlet pressure are calculated;

[0173] Saturated vapor pressure p sat The fitting equation is shown in formula (7):

[0174]

[0175] Condensate mass m vap，sep The calculation is shown in formula (8):

[0176]

[0177] In the formula: m in is the separator inlet flow mass, p sat is the saturated vapor pressure, R is the gas constant 8.314; T is T out，gas ; V sep is the volume of the water separator.

[0178] Gas outlet pressure p out,gas The calculation is shown in formula (9):

[0179]

[0180] Due to the generation of liquid water, the volume of gas that can be accommodated in the steam-water separator will change. The calculation of the volume of the steam-water separator is shown in formula (10):

[0181]

[0182] In the formula: V sep，0 is the initial volume of the separator, V sep is the volume of the water separator, m vap,sep is the quality of condensed water.

[0183] The two-stage steam-water separator model of the present invention is used to calculate its outlet temperature (T sep2，out )T2, then pre-set the secondary steam-water separator model, specifically including the following steps:

[0184] Secondary steam-water separator outlet temperature T sep2，out The calculation formulas for are shown in formula (12) and formula (13):

[0185] Q cl =A×K×(T sep2 -T cl ) (12);

[0186] Q in the formula cl is the heat dissipation of the coolant, T cl is the coolant temperature, A is the heat transfer area, K is the heat transfer coefficient, T sep2 is the internal temperature of the secondary steam-water separator;

[0187]

[0188] In the formula, T sep2,in is the gas temperature at the inlet of the secondary separator, T sep2，out is the outlet gas temperature of the secondary steam-water separator.

[0189] Embodiment 2:

[0190] like Figure 2 and Figure 3 As shown, a PEM water electrolysis hydrogen production system can apply the control method of the PEM water electrolysis hydrogen production system described in Example 1. The hydrogen production system includes an electrolyzer 1, a pre-purification system 100 and a purification system 200.

[0191] A pressure sensor 4 is provided at the cathode outlet of the electrolytic cell 1. The pressure sensor 4 is electrically connected to the parameter input unit. The pressure sensor 4 is used to collect the cathode outlet pressure.

[0192] The pre-purification system 100 includes a primary steam-water separator 2 and a secondary steam-water separator 3. An intake valve 5 is arranged between the gas outlet of the secondary steam-water separator 3 and the gas inlet of the purification system 200. The hydrogen production system also includes a control unit and a parameter input unit, a dynamic relationship establishment unit, a PID closed-loop control unit, a preset unit and an intake control unit which are electrically connected to the control unit respectively. The control unit is also electrically connected to the intake valve 5.

[0193] The parameter input unit is used to obtain the current I, voltage U and cathode outlet pressure of the electrolytic cell 1, and transmit the current I, voltage U and cathode outlet pressure of the electrolytic cell 1 to the dynamic relationship establishment unit. In this embodiment, the parameter input unit may include a human-computer interaction unit, and the current I and voltage U are input by the human-computer interaction unit, and the cathode outlet pressure is collected by the pressure sensor 4.

[0194] The dynamic relationship establishment unit is used to input the current I, voltage U and cathode outlet pressure into a preset mathematical model, and the mathematical model establishes the dynamic relationship between the current I of the electrolytic cell 1, the cathode outlet pressure and the secondary steam-water separator outlet temperature T2, and the mathematical model calculates the coolant flow rate q cl and coolant temperature T cl , and transmitted to the PID closed-loop control unit, see Example 1 for details.

[0195] The PID closed-loop control unit is used to receive the coolant flow rate q cl and coolant temperature T cl , using proportional calculus PID to control the coolant flow q of the secondary steam-water separator cl , so that the outlet temperature T2 of the secondary steam-water separator is stabilized within the required range of the purification system 200.

[0196] The air intake control unit is electrically connected to the control unit; the air intake control unit is used to determine whether the outlet temperature T2 of the secondary steam-water separator is greater than the required temperature T2 of the purification system inlet. ch If the outlet temperature T2 of the secondary steam-water separator is not greater than the required inlet temperature T ch , generate the corresponding opening signal; if the outlet temperature T2 of the secondary steam-water separator is greater than the required temperature T of the purification system inlet ch , generate a corresponding closing signal; finally transmit the opening signal and the closing signal to the control unit, and the control unit controls the intake valve 5 to open according to the opening signal, or controls the intake valve 5 to close according to the closing signal.

[0197] The presetting unit is used to preset the mathematical model, and the specific construction or presetting of the mathematical model is the same as that in the first embodiment.

[0198] like Figure 2 and Figure 3As shown, the PEM water electrolysis hydrogen production system of the present invention collects the current I, voltage U and cathode outlet pressure of the electrolyzer 1 through the parameter input unit, and then transmits them to the dynamic relationship establishment unit, which then establishes the dynamic relationship between the current I of the electrolyzer 1, the cathode outlet pressure and the secondary steam-water separator outlet temperature T2, so as to achieve the cooling and dehumidification of the hydrogen at the outlet of the electrolyzer, and realize the cooling and dehumidification function of the outlet gas temperature. At the same time, the PID closed-loop control unit is used to control the coolant flow of the secondary steam-water separator to ensure that the gas temperature entering the purification system 200 is stable within an appropriate range and meets the conditions for starting the front-end valve of the purification device. In addition, the air intake control unit controls the opening and closing of the air intake valve 5 in real time according to the outlet temperature of the secondary steam-water separator, avoiding the potential damage to the purification system 200 caused by abnormal temperature, ensuring the safety and efficient operation of the entire system, optimizing the gas purification efficiency, and thus achieving efficient operation of the purification device.

[0199] It can be seen that the PEM water electrolysis hydrogen production system of the present invention not only simplifies the control of the pre-purification system 100, provides direct guidance for the development and design of the pre-purification device, but also effectively avoids potential damage to the purification system 200 caused by temperature anomalies, thereby ensuring the overall safety and efficient operation of the system; at the same time, the present invention greatly reduces the layout of sensors, optimizes the design of pre-purification, makes the system structure simple, and ensures the normal operation of the purification system 200.

[0200] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made within the spirit and principles of the present invention, improvements to the equivalent PEM water electrolysis hydrogen production system and its control method, etc., should be included in the protection scope of the present invention.

Claims

1. A control method for a PEM water electrolysis hydrogen production system, wherein the hydrogen production system comprises an electrolyzer, a pre-purification system and a purification system, wherein the pre-purification system comprises a primary steam-water separator and a secondary steam-water separator, and an air intake valve is provided between the air outlet of the secondary steam-water separator and the air inlet of the purification system; characterized in that: The control method comprises the following steps: Step 1, obtaining the current, voltage and cathode outlet pressure of the electrolytic cell; Step 2: inputting current, voltage and cathode outlet pressure into a preset mathematical model to establish a dynamic relationship between the electrolytic cell current, cathode outlet pressure and secondary steam-water separator outlet temperature T2; Step 3: Establish the coolant flow rate q of the secondary steam-water separator cl and coolant temperature T cl The relationship is: Q cl =C cl ×T cl ×q cl , Q in the formula cl is the heat dissipation of the coolant, C cl is the specific heat capacity of the coolant, T cl is the secondary separator coolant temperature, q cl is the coolant flow rate of the secondary water separator; Step 4: Based on the above relationship, proportional calculus PID is used to control the coolant flow rate q of the secondary steam-water separator cl , so that the outlet temperature T2 of the secondary steam-water separator is stable within the range required by the purification system.

2. The control method of the PEM water electrolysis hydrogen production system according to claim 1, characterized in that: The control method further comprises the following steps: Determine whether the outlet temperature T2 of the secondary steam-water separator is greater than T ch ,T ch is the desired temperature at the inlet of the purification system; If the outlet temperature T2 of the secondary steam-water separator is not greater than T ch , open the intake valve; If the secondary steam-water separator outlet temperature T2 is greater than T ch , close the intake valve.

3. The control method of the PEM water electrolysis hydrogen production system according to claim 1, characterized in that: The mathematical model includes an electrolytic cell temperature model, an electrolytic cell flow channel model, a primary steam-water separator model and a secondary steam-water separator model; then the step 2 includes: Input current, voltage and cathode outlet pressure to the electrolytic cell temperature model and electrolytic cell flow channel model; The electrolytic cell temperature model calculates the internal temperature of the electrolytic cell; The electrolyzer flow channel model calculates the hydrogen mole fraction and water mole fraction at the electrolyzer outlet; Input the internal temperature of the electrolyzer, the hydrogen mole fraction, and the water mole fraction to the primary steam-water separator model; The first-stage steam-water separator model calculates the outlet temperature and outlet pressure of the first-stage steam-water separator; Input the outlet temperature and outlet pressure of the first-stage steam-water separator into the second-stage steam-water separator model; The secondary steam-water separator model calculates the secondary steam-water separator outlet temperature T2 to establish a dynamic relationship between the electrolytic cell current, cathode outlet pressure and the secondary steam-water separator outlet temperature T2.

4. The control method of the PEM water electrolysis hydrogen production system according to claim 3, characterized in that: Presetting the electrolytic cell temperature model comprises the following steps: First calculate the coolant flow Q el , Q el =(U el -V th )In cell ; Then calculate the internal temperature T of the electrolytic cell stack , In the formula: U el is the electrolyzer input voltage, V th is the theoretical voltage of a single cell in the electrolytic cell, I is the input current of the electrolytic cell, and n cell is the number of single chambers in the electrolytic cell, T stack is the internal temperature of the electrolytic cell, C stack is the specific heat capacity of the electrolytic cell, q cl0 is the coolant flow in the thermal management water circuit, C cl is the specific heat capacity of the coolant, T stack is the electrolytic cell temperature, T in,PEM is the coolant inlet temperature, Q gas is the heat dissipation.

5. The control method of the PEM water electrolysis hydrogen production system according to claim 3, characterized in that: Presetting the electrolytic cell flow channel model comprises the following steps: According to the mass conservation equation, the changes of hydrogen and water components and water in the electrolyzer flow channel are analyzed; The amount of hydrogen flow rate is equal to the amount of hydrogen at the outlet minus the amount of hydrogen generated; The hydrogen and water in the cathode are calculated using the following formula: In the formula: is the number of moles of hydrogen inside the flow channel, is the number of moles of hydrogen at the inlet, is the number of moles of hydrogen at the outlet, is the number of moles of hydrogen produced by the reaction, is the number of moles of water inside the channel, is the number of moles of water at the inlet, is the number of moles of water at the outlet, is the number of moles of water dragged by the electrons, is the number of moles of diffused water; The partial pressures of hydrogen and water are calculated according to the ideal gas law, and the cathode pressure is equal to the sum of the partial pressures of hydrogen and water; In the formula: is the hydrogen partial pressure, is the number of moles of hydrogen, R is the gas constant, T el is the electrolytic cell temperature, V ca is the volume of the electrolytic cell flow channel, is the water partial pressure, is the number of moles of water at the outlet, P ca is the cathode pressure, is the cathode channel hydrogen partial pressure, is the cathode channel water partial pressure; Mole fraction of hydrogen: Mole fraction of water: The amount of hydrogen produced by the chemical reaction can be calculated in real time based on Faraday’s law; In the formula, n is the number of single chambers, I is the input current of the electrolytic cell, and F is the Faraday constant.

6. The control method of the PEM water electrolysis hydrogen production system according to claim 3, characterized in that: Presetting the primary steam-water separator model comprises the following steps: According to the law of conservation of mass and energy, the temperature and pressure changes caused by the phase change of water inside the first-stage separator are analyzed. According to the law of conservation of mass and the physical structural parameters of the steam-water separator itself, the inlet and water outlet flow equations are established to calculate the gas outlet flow; According to the inference of Bernoulli's equation, the internal pressure drop of the first-stage steam-water separator is proportional to the square of the volume flow rate, and the inlet flow equation can be obtained as shown in formula (1): In the formula: m in is the mass flow rate at the separator inlet, p in is the separator inlet pressure, T in is the separator inlet temperature, p out,gas is the gas outlet pressure of the steam-water separator, Q in,ref is the reference volume flow rate of the water separator, Δp sep,ref is the reference pressure drop of the water separator, M mix is the average molar mass of the mixed gas in the steam-water separator; According to the inference of Bernoulli equation, the water outlet flow equation can be obtained as shown in formula (2): In the formula: m outwater is the water outlet mass flow rate of the steam-water separator, S out,water is the cross-sectional area of ​​the water outlet of the steam-water separator, g is the acceleration due to gravity, L sep is the water level in the steam-water separator; According to the law of conservation of mass and the ideal gas equation, the relationship equation between the inlet and outlet flow rates of the steam-water separator is established as shown in formula (3): In the formula: V sep is the internal volume of the steam-water separator, T out,gas is the gas outlet temperature of the steam-water separator, And T out,gas It is T2, m vap，sep is the water vapor liquefaction flow rate of the steam-water separator, R is the gas constant, M mix is the average molar mass of the mixed gas in the steam-water separator, p out,gas is the gas outlet pressure of the steam-water separator; According to the law of conservation of energy, the calculation equation for the change of enthalpy in the steam-water separator is established to calculate the outlet temperature of the steam-water separator, as shown in formula (4): In the formula: c V_mix is the constant volume specific heat capacity of the mixed gas inside the steam-water separator, m sep is the mass flow rate of the mixed gas at the outlet of the steam-water separator, T sep is the outlet temperature of the steam-water separator, H in is the enthalpy flow rate at the steam-water separator inlet, H LHV is the latent heat of vaporization, H out，vap is the enthalpy of the outlet hydrogen, H out，gas is the enthalpy of outlet water vapor; Calculate the enthalpy flow rate H of the inlet and outlet fluid mix As shown in formula (5): H mix =TΣ(m i c p_i ) (5); The calculation of latent heat of vaporization is shown in formula (6): When the outlet temperature T out,gas Finally, the saturated vapor pressure is calculated according to the saturated vapor pressure fitting equation, and the mass of condensed water and the gas outlet pressure are calculated; The saturated vapor pressure fitting equation is shown in formula (7): The condensed water mass is calculated as shown in formula (8): The calculation of gas outlet pressure is shown in formula (9): Due to the generation of liquid water, the volume of gas that can be accommodated in the steam-water separator will change. The calculation of the volume of the steam-water separator is shown in formula (10): In the formula: V sep,0 is the initial volume of the separator, V sep is the volume of the water separator, m vap,sep is the quality of condensed water.

7. The control method of the PEM water electrolysis hydrogen production system according to claim 3, characterized in that: Presetting the secondary steam-water separator model comprises the following steps: Secondary steam-water separator outlet temperature T sep2,out The calculation formulas for are shown in formula (12) and formula (13): Q cl =A×K×(T sep2 -T cl ) (12); Q in the formula cl is the heat dissipation of the coolant, T cl is the coolant temperature, A is the heat transfer area, K is the heat transfer coefficient, T sep2 is the internal temperature of the secondary steam-water separator; In the formula, T sep2,in is the gas temperature at the inlet of the secondary separator, T sep2,out is the outlet gas temperature of the secondary steam-water separator.

8. A PEM water electrolysis hydrogen production system, comprising an electrolyzer, a pre-purification system and a purification system, wherein the pre-purification system comprises a primary steam-water separator and a secondary steam-water separator, an air intake valve is provided between the air outlet of the secondary steam-water separator and the air inlet of the purification system, characterized in that: The hydrogen production system further comprises a control unit and a parameter input unit, a dynamic relationship establishment unit and a PID closed-loop control unit electrically connected to the control unit respectively, and the control unit is also electrically connected to the intake valve; The parameter input unit is used to obtain the current, voltage and cathode outlet pressure of the electrolytic cell, and transmit the current, voltage and cathode outlet pressure of the electrolytic cell to the dynamic relationship establishment unit; The dynamic relationship establishing unit is used to input the current, voltage and cathode outlet pressure into a preset mathematical model, and the mathematical model establishes the dynamic relationship between the current of the electrolyzer, the cathode outlet pressure and the outlet temperature of the secondary steam-water separator, and the mathematical model calculates and transmits the coolant flow rate q cl and coolant temperature T cl To the PID closed-loop control unit; The PID closed-loop control unit is used to receive the coolant flow rate q cl and coolant temperature T cl , proportional calculus PID is used to control the coolant flow q of the secondary steam-water separator cl , so that the outlet temperature of the secondary steam-water separator is stable within the range required by the purification system.

9. The PEM water electrolysis hydrogen production system according to claim 8, characterized in that: The hydrogen production system further comprises an air intake control unit, which is electrically connected to the control unit; The air intake control unit is used to determine whether the outlet temperature T2 of the secondary steam-water separator is greater than the required temperature of the purification system inlet. If the outlet temperature T2 of the secondary steam-water separator is not greater than the required temperature of the purification system inlet, a corresponding opening signal is generated; if the outlet temperature T2 of the secondary steam-water separator is greater than the required temperature of the purification system inlet, a corresponding closing signal is generated; finally, the air intake control unit transmits the opening signal or the closing signal to the control unit; The control unit controls the intake valve to open according to the received opening signal, and controls the intake valve to close according to the received closing signal.

10. The PEM water electrolysis hydrogen production system according to claim 8, characterized in that: The hydrogen production system further comprises a presetting unit, and the presetting unit is used to pre-set the mathematical model.

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