Drainage method of pre-purification system for PEM water electrolysis hydrogen production

Abstract

The invention discloses a drainage method of a pre-purification system for PEM water electrolysis hydrogen production, which comprises the following steps: acquiring current, voltage and outlet pressure of an electrolytic bath, and then obtaining a first liquid level value and first drainage time of a first-stage steam-water separator and a second liquid level value and second drainage time of a second-stage steam-water separator; whether the first liquid level value and the second liquid level value are larger than the liquid level maximum value or not is judged; if the first liquid level value is larger than the liquid level maximum value, the first drainage valve is opened and timing is started, if the second liquid level value is larger than the liquid level maximum value, the second drainage valve is opened and timing is started, and when the opening time is larger than the first drainage time or the second drainage time, the corresponding drainage valve is closed. Therefore, the dynamic process of accumulation and discharge of the condensate water in the two-stage steam-water separator is calculated by using the operating parameters of the electrolytic cell, so that the start-stop time of the drain valve of the two-stage steam-water separator is dynamically controlled, the accumulated water is discharged, the loss of hydrogen in the drainage process is avoided, and the hydrogen production efficiency of the system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of hydrogen production by electrolysis of water, and in particular to a drainage method of a pre-purification system of PEM hydrogen production by electrolysis of water for solving traveling block failure. 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 hydrogen production efficiency of the PEM water electrolysis hydrogen production system is the key to performance development, and fault diagnosis is the key means to ensure the long life of the system. Therefore, how to control the discharge of condensed water in the two-stage steam-water separator has become a technical problem that technicians in this field urgently need to solve. Summary of the invention

[0006] In view of the above-mentioned shortcomings, the technical problem to be solved by the present invention is to provide a drainage method for a pre-purification system for producing hydrogen by PEM water electrolysis, which can discharge the water accumulated in the two-stage steam-water separator while avoiding the loss of hydrogen during the drainage process, thereby improving the hydrogen production efficiency of the system.

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

[0008] A drainage method for a pre-purification system for producing hydrogen by PEM electrolysis of water, the pre-purification system comprising a primary steam-water separator and a secondary steam-water separator, the drainage outlet of the primary steam-water separator being provided with a first drainage valve, the drainage outlet of the secondary steam-water separator being provided with a second drainage valve, the drainage method comprising the following steps:

[0009] S10, obtaining the current, voltage and cathode outlet pressure of the electrolytic cell;

[0010] S20, obtaining a first liquid level value and a first drainage time of the condensed water in the primary steam-water separator according to the current, voltage and cathode outlet pressure of the electrolytic cell, and then obtaining a second liquid level value and a second drainage time of the condensed water in the secondary steam-water separator;

[0011] S30, determining whether the first liquid level value is greater than the maximum liquid level; determining whether the second liquid level value is greater than the maximum liquid level;

[0012] S40, if the first liquid level value is greater than the maximum liquid level, open the first drain valve and start the first timer;

[0013] If the second liquid level value is greater than the maximum liquid level, the second drain valve is opened and the second timer is started;

[0014] S50, determining whether the timing time of the first timer reaches the first drainage time;

[0015] Determine whether the timing time of the second timer reaches the second drainage time;

[0016] S60, if the timing time of the first timer reaches the first drainage time, close the first drainage valve;

[0017] If the timing time of the second timer reaches the second drainage time, the second drainage valve is closed.

[0018] Preferably, the first-stage steam-water separator is provided with a first liquid level gauge, and the second-stage steam-water separator is provided with a second liquid level gauge; the drainage method further comprises the following steps:

[0019] S45, obtaining a first real-time liquid level indication detected by the first liquid level meter and a second real-time liquid level indication detected by the second liquid level meter;

[0020] S46, determining whether the first real-time liquid level indication is less than the minimum liquid level value;

[0021] Determine whether the second real-time liquid level indication is less than the minimum liquid level value;

[0022] S47, if the first real-time liquid level indication is less than the minimum liquid level value, close the first drain valve;

[0023] If the second real-time liquid level indication is less than the minimum liquid level value, close the first drain valve;

[0024] If the first real-time liquid level indication is not less than the minimum liquid level value, or the second real-time liquid level indication is not less than the minimum liquid level value, execute S50.

[0025] In a preferred embodiment, the S10 includes: obtaining a first liquid level indication detected by a first liquid level meter and a second liquid level indication detected by a second liquid level meter; and the drainage method further includes the following steps:

[0026] S25, determining whether the first liquid level value is within the range of ±n of the first liquid level indication;

[0027] Determine whether the second liquid level value is within the range of ±n of the second liquid level indication;

[0028] S26, if the first liquid level value is not within the range of ±n of the first liquid level indication, or if it is determined that the second liquid level value is not within the range of ±n of the second liquid level indication, stop the machine for inspection;

[0029] S27. If the first liquid level value is within the range of ±n of the first liquid level indication, and the second liquid level value is determined to be within the range of ±n of the second liquid level indication, execute S30.

[0030] Preferably, the step of obtaining the first liquid level value and the first drainage time of the condensed water in the primary steam-water separator in S20 specifically includes:

[0031] S200, activating a pre-built electrolytic cell temperature model, which calculates the electrolytic cell temperature according to the current, voltage and cathode outlet pressure of the electrolytic cell;

[0032] Activate the pre-built electrolyzer flow model, which calculates the number of moles of hydrogen and water in the electrolyzer based on the current, voltage and cathode outlet pressure of the electrolyzer;

[0033] S201. Activate a pre-built first-stage steam-water separator model, which calculates a first liquid level value and a first drainage time of condensed water in the first-stage steam-water separator according to the electrolytic cell temperature, the number of moles of hydrogen, and the number of moles of water.

[0034] Preferably, the step of obtaining the second liquid level value and the second drainage time of the condensed water in the secondary steam-water separator in S20 specifically includes:

[0035] S202, activating a pre-built first-stage steam-water separator model, wherein the first-stage steam-water separator model calculates a first temperature and a first pressure of the first-stage steam-water separator according to the first liquid level value;

[0036] S203, activating a pre-built secondary steam-water separator model, wherein the secondary steam-water separator model calculates a second liquid level value and a second drainage time of condensed water in the secondary steam-water separator according to the first temperature and the first pressure.

[0037] The preferred embodiment is that the first drainage time is equal to the quotient of the accumulated condensed water in the first-stage steam-water separator and the drainage volume at its drainage outlet; the second drainage time is equal to the quotient of the accumulated condensed water in the second-stage steam-water separator and the drainage volume at its drainage outlet.

[0038] Preferably, the construction of the electrolytic cell temperature model includes:

[0039] First calculate the coolant flow Q el , Q el =(U el -V th )In cell ;

[0040] Then calculate the electrolytic cell temperature T stack ,

[0041]

[0042] 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 electrolytic cell temperature, C stack is the specific heat capacity of the electrolytic cell, q cl 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.

[0043] The preferred method is that the electrolytic cell flow channel model is established according to the mass conservation equation to analyze the changes in hydrogen and water components and water in the electrolytic cell flow channel;

[0044] The amount of hydrogen flow rate in the cathode 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:

[0045]

[0046] 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;

[0047] 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;

[0048]

[0049] 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;

[0050] Mole fraction of hydrogen:

[0051]

[0052] Mole fraction of water:

[0053] The amount of hydrogen produced by the chemical reaction can be calculated in real time based on Faraday’s law;

[0054]

[0055] 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.

[0056] Preferably, the first-stage steam-water separator model is constructed, including:

[0057]

[0058] 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;

[0059] According to the inference of Bernoulli equation, the water outlet flow equation can be obtained as shown in formula (2);

[0060]

[0061] In the formula: m out，water 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 water separator, L sep is the first liquid level value.

[0062] Preferably, the construction of the secondary steam-water separator model includes:

[0063] 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);

[0064]

[0065] 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, m vap，sep is the steam liquefaction flow rate of the steam-water separator, 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, R is the gas constant;

[0066] According to the law of conservation of energy, the calculation equation for the enthalpy change in the steam-water separator is established to calculate the outlet temperature of the steam-water separator, as shown in formula (4);

[0067]

[0068] 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,

[0069] H out，vap is the enthalpy of the outlet hydrogen, H out，gas is the enthalpy of outlet water vapor;

[0070] Calculate the enthalpy flow rate of the inlet and outlet fluids as shown in formula (5);

[0071] H mix=T∑(m i c p_i )(5), H mix is the enthalpy flow rate of the inlet and outlet fluids;

[0072] The calculation of latent heat of vaporization is shown in formula (6);

[0073]

[0074] After obtaining the outlet temperature, 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;

[0075] The fitting equation of saturated vapor pressure is shown in formula (7);

[0076]

[0077] The condensed water mass is calculated as shown in formula (8);

[0078]

[0079] The calculation of gas outlet pressure is shown in formula (9);

[0080]

[0081] 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);

[0082]

[0083] 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 condensate quality;

[0084] Liquid level calculation formula:

[0085] In the formula, L sep is the initial liquid level of the water separator, A sep is the bottom area of ​​the water separator.

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

[0087] According to the drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis of the present invention, the current, voltage and cathode outlet pressure of the electrolyzer are obtained; then, according to the current, voltage and cathode outlet pressure of the electrolyzer, the first liquid level value and the first drainage time of the condensed water in the first-stage steam-water separator are obtained, and then the second liquid level value and the second drainage time of the condensed water in the second-stage steam-water separator are obtained; it is judged whether the first liquid level value is greater than the maximum liquid level; it is judged whether the second liquid level value is greater than the maximum liquid level; if the first liquid level value is greater than the maximum liquid level, the first drainage valve is opened and the first timer is started; if the second liquid level value is greater than the maximum liquid level, the second drainage valve is opened and the second timer is started; it is judged whether the timing time of the first timer reaches the first drainage time; it is judged whether the timing time of the second timer reaches the second drainage time; if the timing time of the first timer reaches the first drainage time, the first drainage valve is closed; if the timing time of the second timer reaches the second drainage time, the second drainage valve is closed. It can be seen that the drainage method of the present invention calculates the dynamic process of accumulation and discharge of condensed water in the primary steam-water separator and the secondary steam-water separator through the cathode outlet pressure, input current and voltage of the electrolyzer, thereby dynamically controlling the start and stop times of the drainage valves of the primary steam-water separator and the secondary steam-water separator, thereby discharging the water accumulated in the two-stage steam-water separators while avoiding the loss of hydrogen in the drainage process, thereby improving the hydrogen production efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 is a schematic diagram of an electrolytic cell and a pre-purification system in the present invention;

[0089] Figure 2 It is a schematic flow chart of a drainage method of a pre-purification system for producing hydrogen by PEM water electrolysis in the present invention;

[0090] Figure 3 It is a schematic diagram of the process in the embodiment;

[0091] In the figure: 1-electrolyzer, 2-primary steam-water separator, 3-secondary steam-water separator, 4-first drain valve, 5-second drain valve, 6-first liquid level gauge, 7-second liquid level gauge, 8-pressure sensor, 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] like Figure 1 As shown, a drainage method of a pre-purification system for hydrogen production by PEM water electrolysis, the PEM water electrolysis hydrogen production system includes an electrolyzer 1 and a pre-purification system 200. A pressure sensor is provided at the cathode outlet of the electrolyzer 1, and the pressure sensor can collect the cathode outlet pressure of the electrolyzer 1. The pre-purification system 100 includes a primary steam-water separator 2 and a secondary steam-water separator 3, the drainage port of the primary steam-water separator 2 is provided with a first drainage valve 4, and the drainage port of the secondary steam-water separator 3 is provided with a second drainage valve 5. In this embodiment, a first liquid level gauge (L) 6 is provided on the primary steam-water separator 2, and the first liquid level gauge 6 is used to detect the liquid level of condensed water in the primary steam-water separator 2, and the specific value is the first liquid level indication Ls1; a second liquid level gauge (L) 7 is provided on the secondary steam-water separator 3, and the second liquid level gauge 7 is used to detect the liquid level of condensed water in the secondary steam-water separator 3, and the specific value is the second liquid level indication Ls2. In addition, the gas outlet of the secondary steam-water separator 3 is connected to the gas inlet of the purification system 200 through an air inlet valve.

[0096] like Figure 2 and Figure 3 As shown, the drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis of the present invention comprises the following steps:

[0097] Step S10, 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 collected by the pressure sensor at the cathode outlet of the electrolytic cell. Figure 1 In the figure, I is current, U is voltage, and 8 is pressure sensor (P).

[0099] Step S20, obtaining a first liquid level value L1 and a first drainage time t1 of the condensed water in the first-stage steam-water separator according to the current, voltage and cathode outlet pressure of the electrolytic cell, and then obtaining a second liquid level value L2 and a second drainage time t2 of the condensed water in the second-stage steam-water separator;

[0100] It should be noted that the first liquid level value L1 and the first drainage time t1 can be obtained through a pre-calibrated map table, or can be calculated in real time according to a pre-set mathematical model; similarly, the second liquid level value L2 and the second drainage time t2 can be obtained through a pre-calibrated table, or can be calculated in real time according to a pre-set mathematical model.

[0101] Step S30, determine whether the first liquid level value L1 is greater than the maximum liquid level; determine whether the second liquid level value L2 is greater than the maximum liquid level; wherein the maximum liquid level is the maximum liquid level of the condensed water in the steam-water separator, which can be calibrated in advance. In addition, the comparison between the first liquid level value and the second liquid level value and the maximum liquid level is performed independently and has no correlation with each other.

[0102] Step S40: if the first liquid level value L1 is greater than the maximum liquid level value, that is, the first liquid level value L1>the maximum liquid level value, open the first drain valve and start the first timer;

[0103] If the second liquid level value L2 is greater than the maximum liquid level, that is, when the second liquid level value L2 is greater than the maximum liquid level, the second drain valve is opened and the second timer is started;

[0104] The opening and closing of the first drain valve and the second drain valve are independently controlled and have no relation with each other. When the first liquid level value L1 is greater than the maximum liquid level value, it indicates that the accumulated amount of condensed water in the first-stage steam-water separator has reached the maximum allowable value, which is also the condition for opening the first drain valve; when the second liquid level value L2 is greater than the maximum liquid level value, it indicates that the accumulated amount of condensed water in the second-stage steam-water separator has reached the maximum allowable value, which is also the condition for opening the second drain valve.

[0105] It should be noted that: although the first liquid level value L1 is compared with the maximum liquid level in this step, in fact, when the first liquid level reading checked by the first liquid level meter is greater than the maximum liquid level, the first drain valve is also controlled to open for drainage. Similarly: when the second liquid level reading checked by the second liquid level meter is greater than the maximum liquid level, the second drain valve is also controlled to open for drainage.

[0106] Step S50, determining whether the timing time of the first timer reaches the first drainage time t1;

[0107] Determine whether the timing time of the second timer reaches the second drainage time t2;

[0108] It should be specifically noted that: the first drainage time t1 and the second drainage time t2 can be obtained by looking up from a pre-calibrated map according to the first liquid level value L1 and the second liquid level value L2, or the real-time values can be calculated using a mathematical model.

[0109] Step S60: If the timing time of the first timer reaches the first drainage time t1, that is, the timing time of the first timer > t1, close the first drainage valve;

[0110] If the timing time of the second timer reaches the second drainage time t2, that is, the timing time of the second timer > t2, close the second drainage valve.

[0111] By precisely controlling the drainage time, while ensuring the accumulated water in the two-stage steam-water separator is drained, the loss of hydrogen during the drainage process is avoided, and the hydrogen production efficiency of the system is improved.

[0112] As Figure 1 shown, the drainage method of this embodiment has the following preferred solutions, and the specific steps are as follows:

[0113] Step S10 includes: obtaining the first liquid level reading Ls1 detected by the first liquid level gauge and the second liquid level reading Ls2 detected by the second liquid level gauge;

[0114] Step S25: Determine whether the first liquid level value L1 is within the range of the first liquid level reading ±n, that is, determine whether the following formula holds: Ls1 - n < L1 < Ls1 + n; where n is a real number, and the range of the first liquid level reading ±n is the normal error range of the first liquid level gauge reading. Through this step, the mutual verification between the obtained first liquid level value L1 and the real-time detected first liquid level reading L1 is realized to ensure the accurate detection of the condensate level in the first-stage steam-water separator.

[0115] Determine whether the second liquid level value L2 is within the range of the second liquid level reading ±n, that is, determine whether the following formula holds: Ls2 - n < L2 < Ls2 + n; Similarly, the range of the second liquid level reading ±n is the normal error range of the second liquid level gauge reading Ls2. Through this step, the mutual verification between the obtained second liquid level value L2 and the real-time detected second liquid level reading Ls2 is realized to ensure the accurate detection of the condensate level in the second-stage steam-water separator.

[0116] Step S26: If the first liquid level value L1 is not within the range of the first liquid level reading ±n, or it is determined that the second liquid level value L2 is not within the range of the second liquid level reading ±n, stop the machine for inspection;

[0117] Step S27: If the first liquid level value L1 is within the range of the first liquid level reading ±n, and it is determined that the second liquid level value L2 is within the range of the second liquid level reading ±n, when the first liquid level gauge and the second liquid level gauge are normal, perform the following steps for the liquid level.

[0118] Through the above steps, mutual verification of the liquid level values ​​is achieved. When the liquid level reading detected by the first liquid level gauge or the second liquid level gauge is abnormal, the machine can be stopped for inspection in time to avoid system damage.

[0119] like Figure 1 As shown, the drainage method of this embodiment has the following preferred scheme, and also includes the following steps:

[0120] Step S45, obtaining a first real-time liquid level indication detected by the first liquid level meter and a second real-time liquid level indication detected by the second liquid level meter;

[0121] Step S46, determining whether the first real-time liquid level indication is less than the minimum liquid level value Lmin;

[0122] Determine whether the second real-time liquid level indication is less than the minimum liquid level value Lmin;

[0123] Step S47: If the first real-time liquid level indication is less than the minimum liquid level value Lmin, close the first drain valve;

[0124] If the second real-time liquid level indication is less than the minimum liquid level value Lmin, close the first drain valve;

[0125] If the first real-time liquid level indication is not less than the minimum liquid level value Lmin, or the second real-time liquid level indication is not less than the minimum liquid level value Lmin, execute step S50.

[0126] Through the above steps, it is ensured that during the drainage process when the first drain valve is opened, once the liquid level of the condensed water in the first-stage steam-water separator has reached the minimum liquid level, the first drain valve is closed in time, thereby avoiding the loss of hydrogen during the drainage process and improving the hydrogen production efficiency of the system. Similarly, it is ensured that during the drainage process when the second drain valve is opened, once the liquid level of the condensed water in the second-stage steam-water separator has reached the minimum liquid level, the second drain valve is closed in time, thereby avoiding the loss of hydrogen during the drainage process and improving the hydrogen production efficiency of the system.

[0127] like Figure 2 As shown, in this embodiment, the first liquid level value and the first drainage time step of the condensed water in the primary steam-water separator are obtained in step S20, which specifically includes:

[0128] Step S200, activating a pre-built electrolytic cell temperature model, which calculates the electrolytic cell temperature according to the electrolytic cell current, voltage and cathode outlet pressure;

[0129] Activate the pre-built electrolyzer flow model, which calculates the number of moles of hydrogen and water in the electrolyzer based on the current, voltage and cathode outlet pressure of the electrolyzer;

[0130] Step S201, activating a pre-built first-stage steam-water separator model, the first-stage steam-water separator model calculates a first liquid level value and a first drainage time of condensed water in the first-stage steam-water separator according to the electrolytic cell temperature, the number of moles of hydrogen and the number of moles of water.

[0131] In step S20, a second liquid level value and a second drainage time of the condensed water in the secondary steam-water separator are obtained, which specifically includes:

[0132] Step S202: activating a pre-built first-stage steam-water separator model, wherein the first-stage steam-water separator model calculates a first temperature and a first pressure of the first-stage steam-water separator according to the first liquid level value;

[0133] Step S203, activating the pre-built secondary steam-water separator model, the secondary steam-water separator model calculates the second liquid level value and the second drainage time of the condensed water in the secondary steam-water separator according to the first temperature and the first pressure.

[0134] The drainage method of the pre-purification system for producing hydrogen by electrolysis of water of the present invention mainly obtains the current, voltage and cathode outlet pressure of the electrolyzer, calculates the electrolyzer temperature by using the electrolyzer temperature model, calculates the molar number of hydrogen and water by using the electrolyzer flow channel model, calculates the first liquid level value, the first temperature and the first pressure of the condensed water inside the first-stage steam-water separator by using the first-stage steam-water separator model, and finally calculates the first liquid level value in the second-stage steam-water separator according to the first temperature and the first pressure, that is, the dynamic process of accumulation and discharge of condensed water is calculated by using the above-mentioned model, thereby dynamically controlling the start and stop time of the first drainage valve of the first-stage steam-water separator and the start and stop time of the second drainage valve of the second-stage steam-water separator, avoiding the loss of hydrogen in the drainage process and improving the hydrogen production efficiency of the system; at the same time, because the model can reflect the amount of water storage in real time, the calculated value and the actual indication of the liquid level meter are mutually verified, and the fault situation inside the steam-water separator can be reflected, and the fault can be handled in time.

[0135] like Figure 2 As shown, the electrolyzer flow channel model in this application is used to calculate the molar fraction of hydrogen at its outlet. and the mole fraction of water is

[0136] The electrolytic cell flow channel model is established based on the mass conservation equation to analyze the changes in hydrogen and water components (molar fractions) and water in the electrolytic cell flow channel;

[0137] The cathode is where hydrogen is formed, and the half-reaction equation is:

[0138] 4H + +4e - →H 2 ;

[0139] The amount of hydrogen flow rate in the cathode 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:

[0140]

[0141] 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;

[0142] 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;

[0143]

[0144] 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;

[0145] The mole fraction of hydrogen in the electrolyzer flow channel:

[0146]

[0147] Mole fraction of water:

[0148] Amount of hydrogen produced by chemical reaction Can be calculated in real time according to Faraday's law;

[0149]

[0150] 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.

[0151] The electrolytic cell temperature model in this application is used to calculate the electrolytic cell temperature T stack .

[0152] Specifically, the construction of the electrolytic cell temperature includes:

[0153] First calculate the coolant flow Q el , Q el =(U el -V th )In cell ;

[0154] Then calculate the electrolytic cell temperature T stack ,

[0155]

[0156] 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 electrolytic cell temperature, C stack is the specific heat capacity of the electrolytic cell, q cl 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 amount of heat dissipated by radiation.

[0157] The first-stage steam-water separator model in the present invention is used to calculate the outlet temperature (first temperature T out，gas ) and the first pressure p out，gas .

[0158] Specifically, the construction of the first-stage steam-water separator model includes:

[0159]

[0160] In the formula: m in is the mass flow rate at the steam-water separator inlet, in kg s -1 ;

[0161] p in is the inlet pressure of the steam-water separator, in Pa;

[0162] T in is the steam-water separator inlet temperature, in Pa;

[0163] p out，gas is the gas outlet pressure of the steam-water separator, in Pa;

[0164] Q in，ref is the reference volume flow rate of the water separator, in min L -1 ;

[0165] Δp sep，ref is the reference pressure drop of the steam-water separator, in Pa;

[0166] M mix is the average molar mass of the mixed gas in the steam-water separator, in units of min L -1 .

[0167] According to the inference of Bernoulli equation, the water outlet flow rate m can be obtained out，water The equation is shown in formula (2);

[0168]

[0169] In the formula: m out，water is the water outlet mass flow rate of the steam-water separator,

[0170] S out，water is the cross-sectional area of ​​the water outlet of the steam-water separator,

[0171] g is the acceleration due to gravity,

[0172] L sep is the water level in the water separator, L sep It is the first liquid level value L1.

[0173] In this embodiment, the first drainage time t1 is calculated using the first-stage steam-water separator model. The first drainage time t1 is equal to the quotient of the accumulated condensed water volume in the first-stage steam-water separator and the drainage volume at its drain outlet; m in is the inlet mass flow rate;

[0174] The secondary steam-water separator model in this application is used to calculate the second liquid level value L2;

[0175] Specifically, the construction of the two-stage steam-water separator model includes:

[0176] 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);

[0177]

[0178] In the formula: V sep is the internal volume of the water separator,

[0179] T out，gas is the gas outlet temperature of the steam-water separator,

[0180] m in is the mass flow rate at the steam-water separator inlet, in kg s -1 ,

[0181] m vap，sep is the water vapor liquefaction flow rate of the steam-water separator,

[0182] M mix is the average molar mass of the mixed gas in the steam-water separator,

[0183] p out，gas is the gas outlet pressure of the steam-water separator,

[0184] m out，gas is the gas mass at the outlet of the steam-water separator,

[0185] R is the gas constant;

[0186] According to the law of conservation of energy, the calculation equation of enthalpy change in the steam-water separator is established to calculate the outlet temperature T of the steam-water separator. sep , as shown in formula (4);

[0187]

[0188] In the formula: c V_mix is the constant volume specific heat capacity of the mixed gas inside the steam-water separator,

[0189] m sep is the mass flow rate of mixed gas at the outlet of the steam-water separator,

[0190] T sep is the outlet temperature of the steam-water separator,

[0191] H in is the separator inlet enthalpy flow rate,

[0192] H LHV is the latent heat of vaporization,

[0193] H out，vap is the enthalpy of outlet hydrogen,

[0194] H out，gas is the enthalpy of outlet water vapor;

[0195] Calculate the enthalpy flow rate H of the inlet and outlet fluid mix As shown in formula (5);

[0196] H mix =T∑(m i c p_i ) (5);

[0197] Latent heat of vaporization H LHV The calculation of is shown in formula (6);

[0198]

[0199] When the outlet temperature T out，gasFinally, the saturated vapor pressure is calculated according to the saturated vapor pressure fitting equation, and the mass m of condensed water is calculated. vap，sep ;

[0200] Saturated vapor pressure p sat The fitting equation is shown in formula (7);

[0201]

[0202] Condensate mass m vap，sep Calculation is shown in formula (8);

[0203]

[0204] In the formula: m in is the mass flow rate at the inlet of the secondary separator, p sat is the saturated vapor pressure, R is the gas constant; T is T out，gas ; V sep is the volume of the water separator;

[0205] Gas outlet pressure p out，gas See formula (9) for calculation;

[0206]

[0207] Due to the generation of liquid water, the volume of gas that can be accommodated in the steam-water separator will change. The volume of the steam-water separator V sep The calculation of is shown in formula (10);

[0208]

[0209] 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 condensate quality;

[0210] Liquid level calculation formula:

[0211] In the formula, L sep is the initial liquid level of the water separator, A sep is the bottom area of ​​the water separator.

[0212] In this embodiment, the second drainage time t2 is equal to the quotient of the accumulated condensed water volume in the secondary steam-water separator and the drainage volume at its drainage outlet. It should be particularly noted that the calculation formula for the accumulated condensed water volume in the secondary steam-water separator is the same as that of the secondary steam-water separator.

[0213] In summary, the present invention calculates a mathematical model based on the working current of the electrolyzer and the pressure sensor input located at the outlet of the electrolyzer to analyze the change in the gas-liquid two-phase ratio of water, and calibrates the drain valve opening time through modeling the accumulation and discharge of condensed water in the steam-water separator. The present invention is of great significance for the development of a drainage control strategy for the pre-purification system of the PEM water electrolysis hydrogen production system and the improvement of hydrogen efficiency.

[0214] 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, the drainage method of the pre-purification system of the same PEM water electrolysis hydrogen production, the improvement of the control device and electronic equipment, etc., should be included in the protection scope of the present invention.

Claims

1. A drainage method for a pre-purification system for hydrogen production by PEM water electrolysis, the pre-purification system comprising a primary steam-water separator and a secondary steam-water separator, the drain outlet of the primary steam-water separator being provided with a first drain valve, the drain outlet of the secondary steam-water separator being provided with a second drain valve, characterized in that: The drainage method comprises the following steps: S10, obtaining the current, voltage and cathode outlet pressure of the electrolytic cell; S20, obtaining a first liquid level value and a first drainage time of the condensed water in the primary steam-water separator according to the current, voltage and cathode outlet pressure of the electrolytic cell, and then obtaining a second liquid level value and a second drainage time of the condensed water in the secondary steam-water separator; S30, determining whether the first liquid level value is greater than the maximum liquid level; determining whether the second liquid level value is greater than the maximum liquid level; S40, if the first liquid level value is greater than the maximum liquid level, open the first drain valve and start the first timer; If the second liquid level value is greater than the maximum liquid level, the second drain valve is opened and the second timer is started; S50, determining whether the timing time of the first timer reaches the first drainage time; Determine whether the timing time of the second timer reaches the second drainage time; S60, if the timing time of the first timer reaches the first drainage time, close the first drainage valve; If the timing time of the second timer reaches the second drainage time, the second drainage valve is closed.

2. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 1, characterized in that: The first-stage steam-water separator is provided with a first liquid level gauge, and the second-stage steam-water separator is provided with a second liquid level gauge; the drainage method further comprises the following steps: S45, obtaining a first real-time liquid level indication detected by the first liquid level meter and a second real-time liquid level indication detected by the second liquid level meter; S46, determining whether the first real-time liquid level indication is less than the minimum liquid level value; Determine whether the second real-time liquid level indication is less than the minimum liquid level value; S47, if the first real-time liquid level indication is less than the minimum liquid level value, close the first drain valve; If the second real-time liquid level indication is less than the minimum liquid level value, close the first drain valve; If the first real-time liquid level indication is not less than the minimum liquid level value, or the second real-time liquid level indication is not less than the minimum liquid level value, execute S50.

3. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 2, characterized in that: The S10 includes: obtaining a first liquid level indication detected by a first liquid level meter and a second liquid level indication detected by a second liquid level meter; the drainage method further includes the following steps: S25, determining whether the first liquid level value is within the range of ±n of the first liquid level indication; Determine whether the second liquid level value is within the range of ±n of the second liquid level indication; S26, if the first liquid level value is not within the range of ±n of the first liquid level indication, or if it is determined that the second liquid level value is not within the range of ±n of the second liquid level indication, stop the machine for inspection; S27. If the first liquid level value is within the range of ±n of the first liquid level indication, and the second liquid level value is determined to be within the range of ±n of the second liquid level indication, execute S30.

4. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 1, characterized in that: The step of obtaining the first liquid level value and the first drainage time of the condensed water in the primary steam-water separator in S20 specifically includes: S200, activating a pre-built electrolytic cell temperature model, which calculates the electrolytic cell temperature according to the current, voltage and cathode outlet pressure of the electrolytic cell; Activate the pre-built electrolyzer flow model, which calculates the number of moles of hydrogen and water in the electrolyzer based on the current, voltage and cathode outlet pressure of the electrolyzer; S201. Activate a pre-built first-stage steam-water separator model, which calculates a first liquid level value and a first drainage time of condensed water in the first-stage steam-water separator according to the electrolytic cell temperature, the number of moles of hydrogen, and the number of moles of water.

5. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 4, characterized in that: The step of obtaining the second liquid level value and the second drainage time of the condensed water in the secondary steam-water separator in S20 specifically includes: S202, activating a pre-built first-stage steam-water separator model, wherein the first-stage steam-water separator model calculates a first temperature and a first pressure of the first-stage steam-water separator according to the first liquid level value; S203, activating a pre-built secondary steam-water separator model, wherein the secondary steam-water separator model calculates a second liquid level value and a second drainage time of condensed water in the secondary steam-water separator according to the first temperature and the first pressure.

6. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 5, characterized in that: The first drainage time is equal to the quotient of the accumulated condensed water volume in the first-stage steam-water separator and the drainage volume at its drainage outlet; The second drainage time is equal to the quotient of the accumulated condensed water volume in the secondary steam-water separator and the drainage volume at its drain outlet.

7. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 4, characterized in that: The construction of the electrolytic cell temperature model includes: First calculate the coolant flow Q el , Q el =(U el -V th )In cell ; Then calculate the electrolytic cell temperature T 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 electrolytic cell temperature, C stack is the specific heat capacity of the electrolytic cell, q cl 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.

8. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 4, characterized in that: The electrolytic cell flow channel model is established according to the mass conservation equation to analyze the changes in hydrogen and water components and water in the electrolytic cell flow channel; The amount of hydrogen flow rate in the cathode 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.

9. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 5, characterized in that: The first-stage steam-water separator model is constructed, including: 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 out，water 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 water separator, L sep is the first liquid level value.

10. The drainage method of the pre-purification system for producing hydrogen by PEM water electrolysis according to claim 9, characterized in that: The construction of the secondary steam-water separator model includes: 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, m vap，sep is the steam liquefaction flow rate of the steam-water separator, 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, R is the gas constant; According to the law of conservation of energy, the calculation equation for the enthalpy change 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 of the inlet and outlet fluids as shown in formula (5); H mix =T∑(m i c p_i )(5), H mix is the enthalpy flow rate of the inlet and outlet fluids; The calculation of latent heat of vaporization is shown in formula (6); After obtaining the outlet temperature, 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 condensate quality; Liquid level calculation formula: In the formula, L sep is the initial liquid level of the water separator, A sep is the bottom area of ​​the water separator.

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