Hydrogen production system and method

Abstract

A hydrogen production system and method, relating to the field of water electrolysis for hydrogen production. The system comprises a controller, at least one electrolyser, at least one variable frequency circulating pump, a gas-liquid separation device, and a pressure transmitter. An output end of the gas-liquid separation device is communicated with an input end of each variable frequency circulating pump. An output end of each variable frequency circulating pump is connected to a first end of an alkali liquid return main pipe. A second end of the alkali liquid return main pipe is connected to an input port of each electrolyser. The controller is connected to each electrolyser, each variable frequency circulating pump, and the pressure transmitter, separately. The pressure transmitter is arranged on an alkali liquid return main pipe between at least one electrolyser and at least one variable frequency circulating pump. The controller is used for: determining, on the basis of the number of operating electrolysers, a target variable frequency circulating pump from among the at least one variable frequency circulating pump; and controlling, on the basis of the pressure information collected by the pressure transmitter, the rotation speed of the target variable frequency circulating pump.

Description

Hydrogen production system and method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on July 14, 2023, with application number 202310872521.5 and titled “System and method for preparing hydrogen”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present disclosure relates to the technical field of hydrogen production by water electrolysis, and in particular, to a system and method for preparing hydrogen. Background Art

[0004] Green recovery and the emphasis on renewable energy have become a development consensus in most countries around the world. Hydrogen, as a carrier of renewable energy, is a clean and efficient energy source. Currently, water electrolysis has become a key method for producing hydrogen for industrial use due to its pollution-free production process and high-purity hydrogen. With the rapid development of green electricity and green hydrogen, the energy supply for hydrogen production has shifted from stable grid power to renewable energy sources such as photovoltaics and wind power. Due to the instability of renewable energy, hydrogen production equipment must adapt to the fluctuating characteristics of renewable energy.

[0005] Summary of the Invention

[0006] The purpose of the present disclosure is to provide a hydrogen production system and method for improving the stability of alkali solution flow regulation in an electrolytic cell.

[0007] According to a first aspect of an embodiment of the present disclosure, a hydrogen production system is provided, comprising: a controller, at least one electrolytic cell, at least one variable frequency circulation pump, a gas-liquid separation device, and a pressure transmitter; the output end of the gas-liquid separation device is respectively connected to the input end of each variable frequency circulation pump, the output end of each variable frequency circulation pump is respectively connected to the first end of an alkali liquid return main pipe, the second end of the alkali liquid return main pipe is respectively connected to the input port of each electrolytic cell, the controller is respectively connected to each electrolytic cell, each variable frequency circulation pump, and the pressure transmitter; the pressure transmitter is disposed on the alkali liquid return main pipe between the at least one electrolytic cell and the at least one variable frequency circulation pump;

[0008] The controller is used to:

[0009] determining a target variable frequency circulation pump from at least one variable frequency circulation pump according to the number of operating electrolytic cells;

[0010] According to the pressure information collected by the pressure transmitter, the speed of the target variable frequency circulation pump is controlled, and the pressure information indicates the pressure of the alkali solution return main pipe.

[0011] Optionally, the controller is further configured to:

[0012] When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than the first pressure threshold, an alarm message is issued;

[0013] When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than the second pressure threshold, the electrolytic cell and the variable frequency circulation pump are controlled to stop running, and the second pressure threshold is greater than the first pressure threshold.

[0014] Optionally, the controller is further configured to:

[0015] When the target variable frequency circulation pumps operate at rated power and the pressure information indicates that the pressure of the alkali solution return main pipe is less than the preset pressure, the number of target variable frequency circulation pumps is increased.

[0016] Optionally, there are multiple electrolytic cells, and the system further comprises: multiple alkali liquid flow meters and multiple alkali liquid flow regulating valves, wherein the multiple alkali liquid flow meters and the multiple alkali liquid flow regulating valves are respectively connected to the controller;

[0017] Each electrolytic cell is connected to the alkali liquid return main pipe through an alkali liquid return branch pipe. The first end of each alkali liquid return branch pipe is connected to the input port of the electrolytic cell, and the second end is connected to the second end of the alkali liquid return main pipe. Each alkali liquid return branch pipe is provided with an alkali liquid flow meter and an alkali liquid flow regulating valve.

[0018] Optionally, the controller is further configured to:

[0019] Obtain the alkali solution flow rate detected by each alkali solution flow meter;

[0020] When the alkali liquid flow detected by the target alkali liquid flow meter is not equal to the preset alkali liquid flow rate, the opening of the alkali liquid flow regulating valve corresponding to the target alkali liquid flow meter is controlled to adjust the alkali liquid flow of the alkali liquid return branch pipe where the target alkali liquid flow meter is located to the preset alkali liquid flow rate.

[0021] Optionally, the system further comprises: a plurality of gas-liquid separation components and a plurality of gas purity detection components, each electrolyzer corresponds to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe; each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe are provided with a gas-liquid separation component and a gas purity detection component;

[0022] The first end of each hydrogen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each oxygen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe;

[0023] The controller is also used to:

[0024] Obtaining the gas purity detected by each gas purity detection component;

[0025] When the gas purity detected by the target gas purity detector does not meet the preset purity conditions, adjust the opening of the alkali solution flow control valve corresponding to the target electrolytic cell to adjust the alkali solution flow input to the target electrolytic cell until the gas purity meets the preset purity conditions. The target electrolytic cell is the electrolytic cell corresponding to the target gas purity detector.

[0026] Optionally, the system further comprises: a gas-liquid separation component and a gas purity detection component; each electrolyzer corresponds to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe;

[0027] The first end of each hydrogen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each oxygen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe;

[0028] The hydrogen exhaust main pipe and the oxygen exhaust main pipe are both equipped with a gas-liquid separation component and a gas purity detection component. Each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe is equipped with a shut-off valve, and each shut-off valve is connected to the controller respectively.

[0029] The controller is also used to:

[0030] Open each shut-off valve in turn so that the gas purity detection assembly detects the gas purity of the output gas of each electrolyzer in turn;

[0031] When it is detected that the gas purity does not meet the preset purity conditions, the alkali liquid flow control valve corresponding to the target electrolytic cell is adjusted to adjust the alkali liquid flow input to the target electrolytic cell until the gas purity meets the preset purity conditions. The target electrolytic cell is the electrolytic cell whose gas purity of the output gas does not meet the preset purity conditions.

[0032] Optionally, the preset purity conditions include:

[0033] The hydrogen concentration in the oxygen is less than a first preset concentration threshold; and

[0034] The oxygen concentration in the hydrogen is less than a second preset concentration threshold.

[0035] Optionally, the controller is configured to:

[0036] According to the preset flow step, the opening of the alkali solution flow control valve corresponding to the target electrolytic cell is periodically adjusted until the gas purity meets the preset purity condition.

[0037] According to a second aspect of an embodiment of the present disclosure, a method for preparing hydrogen is provided. The hydrogen preparation system includes: a controller, at least one electrolytic cell, at least one variable frequency circulation pump, a gas-liquid separation device, and a pressure transmitter. The output end of the gas-liquid separation device is respectively connected to the input end of each variable frequency circulation pump, the output end of each variable frequency circulation pump is respectively connected to the first end of the alkali liquid return main pipe, and the second end of the alkali liquid return main pipe is respectively connected to the input port of each electrolytic cell. The controller is respectively connected to each electrolytic cell, each variable frequency circulation pump, and the pressure transmitter. The pressure transmitter is provided on the alkali liquid return main pipe between the at least one electrolytic cell and the at least one variable frequency circulation pump. The method is applied to the hydrogen preparation system and includes:

[0038] determining a target variable frequency circulation pump from at least one variable frequency circulation pump according to the number of operating electrolytic cells;

[0039] The speed of the target variable frequency circulation pump is controlled according to the pressure information collected by the pressure transmitter. The pressure information indicates the pressure of the alkali liquid return main pipe between the electrolytic cell and the gas-liquid separation device.

[0040] Optionally, the method further comprises:

[0041] When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than the first pressure threshold, an alarm message is issued;

[0042] When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than the second pressure threshold, the electrolytic cell and the variable frequency circulation pump are controlled to stop running, and the second pressure threshold is greater than the first pressure threshold.

[0043] Optionally, the method further comprises:

[0044] When the target variable frequency circulation pumps operate at rated power and the pressure information indicates that the pressure of the alkali solution return main pipe is less than the preset pressure, the number of target variable frequency circulation pumps is increased.

[0045] Optionally, there are multiple electrolytic cells, and the system further comprises: multiple alkali liquid flow meters and multiple alkali liquid flow regulating valves, wherein the multiple alkali liquid flow meters and the multiple alkali liquid flow regulating valves are respectively connected to the controller;

[0046] Each electrolytic cell is connected to the alkali liquid return main pipe through an alkali liquid return branch pipe. The first end of each alkali liquid return branch pipe is connected to the input port of the electrolytic cell, and the second end is connected to the second end of the alkali liquid return main pipe. Each alkali liquid return branch pipe is provided with an alkali liquid flow meter and an alkali liquid flow regulating valve.

[0047] Optionally, the method further comprises:

[0048] Obtain the alkali solution flow rate detected by each alkali solution flow meter;

[0049] When the alkali liquid flow detected by the target alkali liquid flow meter is not equal to the preset alkali liquid flow rate, the opening of the alkali liquid flow regulating valve corresponding to the target alkali liquid flow meter is controlled to adjust the alkali liquid flow of the alkali liquid return branch pipe where the target alkali liquid flow meter is located to the preset alkali liquid flow rate.

[0050] Optionally, the system further comprises: a plurality of gas-liquid separation components and a plurality of gas purity detection components, each electrolyzer corresponds to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe; each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe are provided with a gas-liquid separation component and a gas purity detection component;

[0051] The first end of each hydrogen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each oxygen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe;

[0052] The method also includes:

[0053] Obtaining the gas purity detected by each gas purity detection component;

[0054] When the gas purity detected by the target gas purity detector does not meet the preset purity conditions, adjust the opening of the alkali solution flow control valve corresponding to the target electrolytic cell to adjust the alkali solution flow input to the target electrolytic cell until the gas purity meets the preset purity conditions. The target electrolytic cell is the electrolytic cell corresponding to the target gas purity detector.

[0055] Optionally, the system further comprises: a gas-liquid separation component and a gas purity detection component; each electrolyzer corresponds to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe;

[0056] The first end of each hydrogen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each oxygen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe;

[0057] The hydrogen exhaust main pipe and the oxygen exhaust main pipe are both equipped with a gas-liquid separation component and a gas purity detection component. Each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe is equipped with a shut-off valve, and each shut-off valve is connected to the controller respectively.

[0058] The method also includes:

[0059] Open each shut-off valve in turn so that the gas purity detection assembly detects the gas purity of the output gas of each electrolyzer in turn;

[0060] When it is detected that the gas purity does not meet the preset purity conditions, the alkali liquid flow control valve corresponding to the target electrolytic cell is adjusted to adjust the alkali liquid flow input to the target electrolytic cell until the gas purity meets the preset purity conditions. The target electrolytic cell is the electrolytic cell whose gas purity of the output gas does not meet the preset purity conditions.

[0061] Optionally, the gas purity not meeting the preset purity condition includes at least one of the following:

[0062] The hydrogen concentration in the oxygen is greater than or equal to a first preset concentration threshold;

[0063] The oxygen concentration in the hydrogen is greater than or equal to a second preset concentration threshold.

[0064] Optionally, adjusting the opening of the alkali solution flow control valve corresponding to the target electrolytic cell includes:

[0065] According to the preset flow step, the opening of the alkali solution flow control valve corresponding to the target electrolytic cell is periodically adjusted.

[0066] According to the above technical solution, the hydrogen production system disclosed herein includes: a controller, at least one electrolyzer, at least one variable-frequency circulation pump, a gas-liquid separation device, and a pressure transmitter. The output end of the gas-liquid separation device is connected to the input end of each variable-frequency circulation pump, the output end of each variable-frequency circulation pump is connected to the first end of the alkali solution return main pipe, and the second end of the alkali solution return main pipe is connected to the input port of each electrolyzer. The controller is connected to each electrolyzer, each variable-frequency circulation pump, and the pressure transmitter. The pressure transmitter is disposed on the alkali solution return main pipe between the at least one electrolyzer and the at least one variable-frequency circulation pump. The controller is configured to determine a target variable-frequency circulation pump from the at least one variable-frequency circulation pump based on the number of operating electrolyzers, and control the speed of the target variable-frequency circulation pump based on the pressure information collected by the pressure transmitter to maintain a constant pressure in the alkali solution return main pipe. This ensures that the electrolyzer inputs alkali solution at a constant pressure, making alkali solution flow regulation in the electrolyzer more stable and accurate, and reducing the impact of alkali solution on the pump caused by load fluctuations.

[0067] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0069] FIG1 is a block diagram of a hydrogen production system according to an exemplary embodiment;

[0070] FIG2 is a schematic diagram of a hydrogen production system according to an exemplary embodiment;

[0071] FIG3 is a schematic diagram showing a control strategy for alkali solution flow according to an exemplary embodiment;

[0072] FIG4 is a schematic diagram of another hydrogen production system according to an exemplary embodiment;

[0073] FIG5 is a schematic diagram showing another control strategy for alkali solution flow according to an exemplary embodiment;

[0074] FIG6 is a schematic diagram showing another control strategy for alkali solution flow according to an exemplary embodiment;

[0075] FIG7 is a flow chart showing a method for producing hydrogen according to an exemplary embodiment;

[0076] FIG8 is a flow chart showing another method for producing hydrogen according to an exemplary embodiment;

[0077] FIG9 is a flow chart showing another method for producing hydrogen according to an exemplary embodiment;

[0078] FIG10 is a flow chart showing another method for producing hydrogen according to an exemplary embodiment;

[0079] FIG11 is a flow chart showing another method for producing hydrogen according to an exemplary embodiment;

[0080] FIG12 is a flow chart showing another method for producing hydrogen according to an exemplary embodiment.

[0081] Explanation of the reference numerals 100 - hydrogen preparation system; 101 - controller; 102 - electrolytic cell; 103 - variable frequency circulation pump; 104 - gas-liquid separation device; 1041 - hydrogen side gas-liquid separation unit; 1042 - oxygen side gas-liquid separation unit; 105 - pressure transmitter; 106 - alkali liquid return main pipe; 107 - alkali liquid cooler. DETAILED DESCRIPTION

[0082] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0083] FIG1 is a block diagram of a hydrogen production system according to an exemplary embodiment. As shown in FIG1 , system 100 includes a controller 101, at least one electrolytic cell 102, at least one variable-frequency circulation pump 103, a gas-liquid separator 104, and a pressure transmitter 105. The output of gas-liquid separator 104 is connected to the input of each variable-frequency circulation pump 103. The output of each variable-frequency circulation pump 103 is connected to the first end of an alkali solution return manifold 106, the second end of which is connected to the input of each electrolytic cell 102. Controller 101 is connected to each electrolytic cell 102, each variable-frequency circulation pump 103, and pressure transmitter 105. Pressure transmitter 105 is located on alkali solution return manifold 106 between at least one electrolytic cell 102 and at least one variable-frequency circulation pump 103.

[0084] The controller 101 is used to:

[0085] Determining a target variable frequency circulation pump 103 from at least one variable frequency circulation pump 103 according to the number of operating electrolytic cells 102 ;

[0086] The speed of the target variable frequency circulation pump 103 is controlled according to the pressure information collected by the pressure transmitter 105 , and the pressure information indicates the pressure of the alkali solution return main pipe 106 .

[0087] For example, the gas-liquid separation device 104 in the present disclosure may include a hydrogen side gas-liquid separation unit 1041 and an oxygen side gas-liquid separation unit 1042. The hydrogen side gas-liquid mixture produced by each electrolytic cell 102 enters the hydrogen side gas-liquid separation unit 1041 for separation, and the oxygen side gas-liquid mixture produced by each electrolytic cell 102 enters the oxygen side gas-liquid separation unit 1042 for separation. The separated alkali liquid is returned to each electrolytic cell 102 from the gas-liquid separation device 104 through the alkali liquid return main pipe 106.

[0088] The variable frequency circulation pump 103 in the present disclosure may be a variable frequency circulation pump, or may include a frequency converter and an alkali solution circulation pump, wherein the controller 101 may control the speed of the alkali solution circulation pump by controlling the frequency of the frequency converter, which is not specifically limited in the present disclosure.

[0089] In some embodiments, there can be one electrolytic cell 102 and one variable frequency circulation pump 103, and the target variable frequency circulation pump 103 is the variable frequency circulation pump 103. The output ends of the gas-liquid separation device 104 are respectively connected to the input ends of the variable frequency circulation pump 103; wherein, the output ends of the gas-liquid separation device 104 can be directly connected to the input ends of the variable frequency circulation pump 103; the output ends of the gas-liquid separation device 104 can also be first connected to the first ends of the alkali liquid cooler 107, and the second end of the alkali liquid cooler can be connected to the input end of the variable frequency circulation pump 103, that is, an alkali liquid cooler can also be connected between the gas-liquid separation device 104 and the variable frequency circulation pump 103. The present disclosure does not specifically limit the communication method between the gas-liquid separation device 104 and the variable frequency circulation pump 103. The output end of the variable frequency circulation pump 103 is connected to the first end of the alkali liquid return main pipe 106, the second end of which is connected to the input port of the electrolytic cell 102. A pressure transmitter 105 is installed on the alkali liquid return main pipe 106 between the electrolytic cell 102 and the variable frequency circulation pump 103. The gas-liquid mixture produced by the electrolytic cell 102 enters the gas-liquid separator 104 for separation. The separated alkali liquid is then returned to the electrolytic cell 102 from the gas-liquid separator 104 through the alkali liquid return main pipe 106. The pressure transmitter 105 can detect the pressure of the alkali liquid return main pipe 106 in real time. When the pressure transmitter 105 detects that the pressure value of the alkali liquid return main pipe 106 is less than the preset pressure, the pressure information is sent to the controller 101. The controller 101 can perform PID (Proportional Integral Derivative) adjustment based on the detected pressure value and the preset pressure, increase the frequency of the variable frequency circulation pump 103, and correspondingly increase the speed of the variable frequency circulation pump 103 to maintain the pressure of the alkali liquid return main pipe 106 at the preset pressure. When the pressure transmitter 105 detects that the pressure value of the alkali liquid return main pipe 106 is greater than the preset pressure, the pressure information is sent to the controller 101. The controller 101 can perform PID adjustment based on the detected pressure value and the preset pressure, reduce the frequency of the variable frequency circulation pump 103, and correspondingly reduce the speed of the variable frequency circulation pump 103. That is, when the outlet demand flow of the variable frequency circulation pump 103 changes (for example, when the starting number of the electrolytic cell 102 changes), the outlet pressure of the variable frequency circulation pump 103 will change accordingly. At this time, it is necessary to change the speed of the variable frequency circulation pump 103 to adjust the outlet pressure of the variable frequency circulation pump 103, so as to maintain the pressure of the alkali solution return liquid main pipe 106 at the preset pressure.

[0090] In other embodiments, there may be multiple electrolytic cells 102 and a single variable-frequency circulation pump 103. The target variable-frequency circulation pump 103 is the variable-frequency circulation pump 103. Each electrolytic cell 102 corresponds to a corresponding alkali solution return branch pipe. Each electrolytic cell 102 is connected to an alkali solution return main pipe 106 via an alkali solution return branch pipe. The first end of each alkali solution return branch pipe is connected to the input port of the electrolytic cell 102, and the second end of each alkali solution return branch pipe is connected to the second end of the alkali solution return main pipe 106. The first end of the alkali solution return main pipe 106 is connected to the output end of the variable-frequency circulation pump 103, and the output end of the gas-liquid separator 104 is connected to the input end of the variable-frequency circulation pump 103. The gas-liquid mixture generated in the electrolytic cell 102 enters the gas-liquid separator 104 for separation. The separated alkali solution is then returned from the gas-liquid separator 104 to each electrolytic cell 102 via the alkali solution return main pipe 106 and each alkali solution return branch pipe. The pressure transmitter 105 can be set on the alkali liquid return main pipe 106 between the multiple electrolytic cells 102 and the variable frequency circulation pump 103 to detect the pressure of the alkali liquid return main pipe 106 in real time and send the pressure information of the alkali liquid return main pipe 106 to the controller 101. The controller 101 can perform PID adjustment according to the pressure information and the preset pressure, and maintain the pressure of the alkali liquid return main pipe 106 at the preset pressure by controlling the speed of the variable frequency circulation pump 103.

[0091] In other embodiments, there may be multiple electrolytic cells 102 and multiple variable frequency circulation pumps 103. The rated powers of the multiple variable frequency circulation pumps may be the same or different. When the adjustment range of the alkali liquid flow rate is large, the pressure of the alkali liquid return main pipe will also fluctuate within a larger range. Preferably, variable frequency circulation pumps with different rated powers are used in combination to achieve more accurate adjustment of the pressure of the alkali liquid return main pipe. Each electrolytic cell 102 corresponds to an alkali liquid return branch pipe, and each electrolytic cell 102 is connected to the alkali liquid return main pipe 106 via the alkali liquid return branch pipe. The first end of each alkali liquid return branch pipe is connected to the input port of the corresponding electrolytic cell 102, and the second end of each alkali liquid return branch pipe is connected to the second end of the alkali liquid return main pipe 106. The first end of the alkali liquid return main pipe 106 is respectively connected to the output end of each variable frequency circulation pump 103, and the output end of the gas-liquid separation device 104 is connected to the input end of the variable frequency circulation pump 103. The gas-liquid mixture produced by the electrolytic cells 102 enters the gas-liquid separation device 104 for separation. The separated alkali liquor is then returned from the gas-liquid separation device 104 to each electrolytic cell 102 via the alkali liquor return main pipe 106 and each alkali liquor return branch pipe. A pressure transmitter 105 can be installed on the alkali liquor return main pipe 106 between the multiple electrolytic cells 102 and the variable frequency circulation pumps 103 to monitor the pressure of the alkali liquor return main pipe 106 in real time and transmit this pressure information to the controller 101. The controller 101 can determine a target variable frequency circulation pump 103 from the multiple variable frequency circulation pumps 103 based on the number of operating electrolytic cells 102. Specifically, this includes determining the number of target variable frequency circulation pumps to be activated and the rated power of the target variable frequency circulation pump to be activated. The controller 101 then performs PID control based on this pressure information and a preset pressure, controlling the speed of the target variable frequency circulation pump 103 to maintain the pressure in the alkali liquor return main pipe 106 at the preset pressure.

[0092] In summary, the hydrogen production system disclosed herein includes a controller, at least one electrolyzer, at least one variable-frequency circulation pump, a gas-liquid separation device, and a pressure transmitter. The output end of the gas-liquid separation device is connected to the input end of each variable-frequency circulation pump, the output end of each variable-frequency circulation pump is connected to the first end of an alkali solution return main pipe, and the second end of the alkali solution return main pipe is connected to the input port of each electrolyzer. The controller is connected to each electrolyzer, each variable-frequency circulation pump, and the pressure transmitter. The pressure transmitter is disposed on the alkali solution return main pipe between the at least one electrolyzer and the at least one variable-frequency circulation pump. The controller is configured to determine a target variable-frequency circulation pump from the at least one variable-frequency circulation pump based on the number of operating electrolyzers, and control the speed of the target variable-frequency circulation pump based on pressure information collected by the pressure transmitter to maintain a constant pressure in the alkali solution return main pipe. This ensures that the electrolyzers input alkali solution at a constant pressure, making alkali solution flow regulation in the electrolyzers more stable and accurate, and reducing the impact of alkali solution on the pumps caused by load fluctuations. At the same time, the purpose of saving electric energy is achieved by interlocking the speed of the variable frequency circulation pump with the pressure of the alkali solution return pipe 106.

[0093] According to some embodiments of the present disclosure, the controller 101 is further configured to:

[0094] When the pressure information indicates that the pressure of the alkali solution return pipe 106 is greater than the first pressure threshold, an alarm message is issued;

[0095] When the pressure information indicates that the pressure of the alkali solution return pipe 106 is greater than the second pressure threshold, the electrolytic cell 102 and the variable frequency circulation pump 103 are controlled to stop running, and the second pressure threshold is greater than the first pressure threshold.

[0096] For example, when the electrolytic cell 102 is operating at a low load, the required alkali solution flow rate is small. Accordingly, the alkali solution retained in the alkali solution return main pipe 106 will increase, resulting in excessive pressure in the alkali solution return main pipe 106. If the pressure information indicates that the pressure of the alkali solution return main pipe 106 is greater than a first pressure threshold, an alarm can be issued to indicate that the pressure of the alkali solution return main pipe 106 is too high, wherein the first pressure threshold can be the maximum rated operating pressure of the variable frequency circulation pump 103. If the pressure information indicates that the pressure of the alkali solution return main pipe 106 is greater than a second pressure threshold, indicating that the current operating state is prone to safety accidents, the electrolytic cell 102 and the variable frequency circulation pump 103 can be controlled to stop operating, wherein the second pressure threshold is greater than the first pressure threshold. The second pressure threshold is set according to the needs of the hydrogen production system and is not limited to one or certain specific values.

[0097] According to other embodiments of the present disclosure, the controller 101 is further configured to:

[0098] When the target variable-frequency circulation pumps 103 are operating at rated power and the pressure information indicates that the pressure of the alkali solution return main pipe 106 is less than a preset pressure, the number of target variable-frequency circulation pumps 103 is increased. As described above, the rated power of the target variable-frequency circulation pumps 103 is selected based on the required adjustment range of the alkali solution flow rate of the hydrogen production system and is not limited to one or more specific values.

[0099] When it is detected that the pressure of the alkali solution return main pipe 106 is less than the preset pressure, it means that the flow demand of the electrolyte has increased, resulting in the current alkali solution amount in the alkali solution return main pipe 106 no longer meeting the demand. At this time, if it is detected that the target variable frequency circulation pump 103 is already operating at the rated power, in order to ensure the normal operation of the variable frequency circulation pump, the number of variable frequency circulation pumps 103 needs to be increased to increase the amount of alkali solution pumped out, that is, to increase the amount of alkali solution in the alkali solution return main pipe 106, so that the pressure of the alkali solution return main pipe 106 can be restored to the preset pressure.

[0100] For example, as shown in Figure 2, 121, 122, 123, 124, and 125 are alkali solution flow meters No. 1 to 5; 131, 132, 133, 134, and 135 are alkali solution flow control valves No. 1 to 5; and 107 is a alkali solution cooler. There are five electrolytic cells 102 and three variable frequency circulation pumps 103. Accordingly, the control strategy for the variable frequency circulation pumps 103 and alkali solution flow is shown in Figure 3. When the number of electrolytic cells 102 started (N) is less than or equal to 3, the outlet flow demand of the variable frequency circulation pumps 103 is relatively low, and the target variable frequency circulation pump 103 can be one. That is, one of the three variable frequency circulation pumps 103 is in operation, while the other two are in shutdown. When the starting number of electrolytic cells 102 is 4≤N≤5, the increased number of electrolytic cells leads to an increase in the outlet demand flow rate of the variable frequency circulation pump 103, which causes the pressure of the alkali solution return main pipe 106 to decrease, thereby requiring an increase in the number of target variable frequency circulation pumps 103. At this time, the target variable frequency circulation pumps 103 can be 2, that is, 2 of the 3 variable frequency circulation pumps 103 are in operation, and the other 1 variable frequency circulation pump 103 is in a shutdown state. As a backup pump, the backup pump can be started when the 2 variable frequency circulation pumps 103 in operation fail.

[0101] As shown in Figure 4 , 120, 121, 122, 123, 124, and 125 are alkali solution flow meters No. 1 to 6; 130, 131, 132, 133, 134, and 135 are alkali solution flow control valves No. 1 to 6; and 107 is a alkali solution cooler. There are six electrolytic cells 102 and four variable frequency circulation pumps 103. Accordingly, the control strategy for the variable frequency circulation pumps 103 and alkali solution flow is shown in Figure 5 . When the number of electrolytic cells 102 started (N) is less than or equal to 2, the outlet flow demand of the variable frequency circulation pumps 103 is relatively low, and the target variable frequency circulation pump 103 can be one. That is, one of the four variable frequency circulation pumps 103 is in operation, while the other three are in shutdown. When the number of electrolytic cells 102 started is 3≤N≤4, the increased number of electrolytic cells causes the outlet flow rate of the variable frequency circulation pump 103 to increase, which causes the pressure of the alkali solution return pipe 106 to decrease, thereby requiring an increase in the number of target variable frequency circulation pumps 103. In this case, the target variable frequency circulation pumps 103 can be two, that is, two of the four variable frequency circulation pumps 103 are in operation, and the other two are in a stopped state. Similarly, when the number of electrolytic cells 102 started is 5≤N≤6, the target variable frequency circulation pumps 103 can be three, that is, three of the four variable frequency circulation pumps 103 are in operation, and the other one is in a stopped state, serving as a backup pump.

[0102] According to other embodiments of the present disclosure, there are multiple electrolytic cells 102, and the system 100 further includes: multiple alkali liquid flow meters and multiple alkali liquid flow regulating valves, each of which is connected to the controller 101. Each electrolytic cell 102 can be connected to the alkali liquid return main pipe 106 via an alkali liquid return branch pipe, with a first end of each alkali liquid return branch pipe connected to the input port of the electrolytic cell 102 and a second end connected to the second end of the alkali liquid return main pipe 106. Each alkali liquid return branch pipe is provided with an alkali liquid flow meter and an alkali liquid flow regulating valve.

[0103] The controller 101 is further configured to:

[0104] Obtain the alkali solution flow rate detected by each alkali solution flow meter;

[0105] When the alkali liquid flow detected by the target alkali liquid flow meter is not equal to the preset alkali liquid flow rate, the opening of the alkali liquid flow regulating valve corresponding to the target alkali liquid flow meter is controlled to adjust the alkali liquid flow of the alkali liquid return branch pipe where the target alkali liquid flow meter is located to the preset alkali liquid flow rate.

[0106] For example, when there are multiple electrolyzers 102, an alkali liquid flow meter and an alkali liquid flow regulating valve can be provided on the alkali liquid return branch pipe corresponding to each electrolyzer 102, wherein each alkali liquid flow meter can detect the alkali liquid flow of the corresponding alkali liquid return branch pipe in real time, and the alkali liquid flow regulating valve can be a ball valve or a pneumatic diaphragm regulating valve. During the operation of the electrolyzer 102, due to the volatility of the power supply, the electrolyzer 102 will have a low-load operating condition. When the electrolyzer 102 is running at a low load, due to the reduction in hydrogen production, the oxygen purity or hydrogen purity will decrease. By providing an alkali liquid flow meter and an alkali liquid flow regulating valve on the alkali liquid return branch pipe corresponding to each electrolyzer 102, the alkali liquid flow can be automatically adjusted for the electrolyzer 102 in low-load operation, achieving point-to-point regulation, reducing the alkali liquid flow output from the electrolyzer 102, and improving gas purity. The electrolytic cell 102 needs to meet the following conditions during low-load operation: 1) the load of the electrolytic cell 102 is greater than the load linkage value; 2) the alkali solution flow rate is greater than the alkali solution flow rate linkage value; 3) the temperature at the outlet of the electrolytic cell 102 is less than the cell temperature linkage value. The load linkage value refers to the minimum operating load of the electrolytic cell, which is usually 20%-30% of the rated load of the electrolytic cell; the alkali solution flow rate linkage value refers to the minimum flow rate of the alkali solution, which is usually determined by the minimum operating load of the electrolytic cell, that is, it can be determined based on the load linkage value of the electrolytic cell and is not limited to a specific value or values; the cell temperature linkage value refers to the maximum operating temperature in the electrolytic cell, which is determined by the performance of the electrolytic cell and is usually a value between 90-150°C and is not limited to a specific value or values.

[0107] In some embodiments, the controller 101 may pre-set a preset operating power for each electrolyzer 102 and determine a preset alkali solution flow rate corresponding to each alkali solution return branch according to the preset operating power of each electrolyzer 102. The preset operating power of the electrolyzer is determined by the hydrogen production capacity of the electrolyzer and may be determined according to the rated power of the electrolyzer. The hydrogen production capacity of the electrolyzer 102 may be 100-5000 Nm 3 / h. During the process of hydrogen production by electrolysis of water, the controller 101 can obtain the alkali liquid flow rate detected by each alkali liquid flow meter. If the alkali liquid flow rate detected by the target alkali liquid flow meter is not equal to the preset alkali liquid flow rate, PID control can be performed based on the alkali liquid flow rate detected by the target alkali liquid flow meter and the preset alkali liquid flow rate. By controlling the opening of the alkali liquid flow regulating valve corresponding to the target alkali liquid flow meter, the alkali liquid flow rate of the alkali liquid return branch pipe where the target alkali liquid flow meter is located is adjusted to the preset alkali liquid flow rate. In this way, the alkali liquid flow rate of each electrolytic cell 102 can always be maintained at the set preset alkali liquid flow rate, thereby improving the gas purity and reducing the emission of unqualified gases.

[0108] According to other embodiments of the present disclosure, the system 100 further includes: a plurality of gas-liquid separation components and a plurality of gas purity detection components, and each electrolyzer 102 corresponds to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe. Each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe are provided with a gas-liquid separation component and a gas purity detection component. The first end of each hydrogen exhaust branch pipe is connected to the output port of the electrolyzer 102, and the second end is connected to the hydrogen exhaust main pipe. The first end of each oxygen exhaust branch pipe is connected to the output port of the electrolyzer 102, and the second end is connected to the oxygen exhaust main pipe.

[0109] The controller 101 is further configured to:

[0110] Obtaining the gas purity detected by each gas purity detection component;

[0111] When the gas purity detected by the target gas purity detector does not meet the preset purity conditions, adjust the opening of the alkali solution flow control valve corresponding to the target electrolytic cell 102 corresponding to the target gas purity detector to adjust the alkali solution flow input to the target electrolytic cell 102 until the gas purity meets the preset purity conditions.

[0112] For example, as shown in Figure 6, during the startup of the equipment, due to the large fluctuations in hydrogen production from renewable energy power generation, when the load of the electrolytic cell 102 is in a low-load operating condition, the actual operating power of the electrolytic cell 102 is low, and the purity of the prepared gas will be low. At this time, it is necessary to automatically and finely adjust the alkali solution flow rate for each electrolytic cell 102 to improve the purity of the gas.

[0113] In the case where there are multiple electrolytic cells 102, each electrolytic cell 102 may correspond to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe, and each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe are provided with a gas-liquid separation component and a gas purity detection component to analyze the purity of the gas produced by each electrolytic cell 102, and then accurately adjust the alkaline liquid flow rate of each electrolytic cell 102 according to the purity detection results. Among them, the gas purity detection component is used to detect the purity of the gas discharged from the electrolytic cell 102, and the gas purity detection component can be, for example, a gas analyzer. The gas-liquid separation component is used to separate the gas discharged from each electrolytic cell 102 by gas and liquid to remove the alkaline mist, so as to prevent the alkali carried by the exhaust gas from damaging the gas purity detection component.

[0114] Since the lower the alkali liquid flow rate in the electrolyzer 102, the more thorough the separation of hydrogen in the hydrogen gas-liquid separation unit and the more thorough the gas-liquid separation of oxygen in the oxygen gas-liquid separation unit, the higher the purity of hydrogen and oxygen. As shown in Figure 6, after the controller 101 obtains the gas purity detected by each gas purity detection component, if it is determined that the gas purity detected by the target gas purity detector does not meet the preset purity condition, the opening of the alkali liquid flow regulating valve corresponding to the target electrolyzer 102 corresponding to the target gas purity detector can be adjusted to reduce the alkali liquid flow rate input to the target electrolyzer 102, thereby improving the purity of the gas discharged from the electrolyzer 102. In the process of reducing the alkali liquid flow rate input to the target electrolyzer 102, once it is detected that the gas purity meets the preset purity condition, the reduction process can be stopped, as long as it is ensured that the water electrolysis hydrogen production system 100 can output hydrogen with a purity that meets the corresponding requirements to avoid the electrolyte flow being too low.

[0115] According to other embodiments of the present disclosure, the system 100 further includes: a gas-liquid separation component and a gas purity detection component. Each electrolyzer 102 corresponds to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe. The first end of each hydrogen exhaust branch pipe is connected to the output port of the electrolyzer 102, and the second end is connected to the hydrogen exhaust main pipe. The first end of each oxygen exhaust branch pipe is connected to the output port of the electrolyzer 102, and the second end is connected to the oxygen exhaust main pipe. A gas-liquid separation component and a gas purity detection component are provided on the hydrogen exhaust main pipe and the oxygen exhaust main pipe, and a shut-off valve is provided on each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe, and each shut-off valve is respectively connected to the controller 101.

[0116] The controller 101 is further configured to:

[0117] Open each shut-off valve in sequence so that the gas purity detection assembly detects the gas purity of the gas output from each electrolytic cell 102 in sequence;

[0118] When it is detected that the gas purity does not meet the preset purity conditions, the opening of the alkali liquid flow control valve corresponding to the target electrolytic cell 102 is adjusted to adjust the alkali liquid flow input to the target electrolytic cell 102 until the gas purity meets the preset purity conditions. The target electrolytic cell 102 is the electrolytic cell 102 whose gas purity of the output gas does not meet the preset purity conditions.

[0119] For example, the gas-liquid separation component and the gas purity detection component can be arranged on the hydrogen exhaust main pipe and the oxygen exhaust main pipe, and a shut-off valve is arranged on each hydrogen exhaust main pipe and each oxygen exhaust main pipe, and each shut-off valve is respectively connected to the controller 101. The controller 101 can open each shut-off valve in sequence according to a preset cycle. When the shut-off valve corresponding to a certain electrolyzer 102 is opened, the other shut-off valves are in a closed state, so that the hydrogen discharged from the electrolyzer 102 can be discharged through the hydrogen exhaust branch pipe to the hydrogen exhaust main pipe, and the oxygen can be discharged through the oxygen exhaust branch pipe to the oxygen exhaust main pipe. At this time, the gas purity detection component arranged on the hydrogen exhaust main pipe can detect the purity of the hydrogen discharged from the electrolyzer 102, and the gas purity detection component arranged on the oxygen exhaust main pipe can detect the purity of the oxygen discharged from the electrolyzer 102. In this way, by opening each shut-off valve in turn, the gas purity detection component can detect the gas purity of the gas output by each electrolytic cell 102 in turn. There is no need to respectively set a gas-liquid separation component and a gas purity detection component on each hydrogen exhaust branch and oxygen exhaust branch, which can reduce production costs.

[0120] The preset purity condition refers to the concentration of impurity gases in the gas being below a certain concentration threshold, including the following two conditions: 1) the hydrogen concentration in the oxygen is less than a first preset concentration threshold; and 2) the oxygen concentration in the hydrogen is less than a second preset concentration threshold. The first preset concentration threshold may be 1.5%, and the second preset concentration threshold may be 0.5%.

[0121] According to other embodiments of the present disclosure, the controller 101 is configured to:

[0122] The opening of the alkali solution flow control valve corresponding to the target electrolytic cell 102 is periodically adjusted according to a preset flow step size until the gas purity meets the preset purity condition. The flow step size refers to the number of intervals in which the required alkali solution flow adjustment value is divided to meet the preset purity condition, with the adjustment value for each interval being the step size. Within one cycle, the opening of the alkali solution flow control valve is adjusted according to one preset flow step size.

[0123] For example, in the process of reducing the alkali liquid flow rate input to the target electrolytic cell 102, the reduction of the alkali liquid flow rate and the judgment of the gas purity can be performed periodically according to a preset flow step size, and the alkali liquid flow rate is controlled to be reduced by a preset flow step size in each cycle, and then it is judged whether the gas purity meets the preset purity condition. If the gas purity meets the preset purity condition, then the reduction of the alkali liquid flow rate can be stopped. If the gas purity does not meet the preset purity condition, then the alkali liquid flow rate can continue to be reduced according to the preset flow step size until the gas purity meets the preset purity condition. Among them, the length of each cycle can be determined according to its specific application environment, and the preset flow step size of each cycle can be the same or different, and the present disclosure does not make specific limitations on this.

[0124] In summary, the hydrogen production system disclosed herein includes a controller, at least one electrolyzer, at least one variable-frequency circulation pump, a gas-liquid separation device, and a pressure transmitter. The output end of the gas-liquid separation device is connected to the input end of each variable-frequency circulation pump, the output end of each variable-frequency circulation pump is connected to the first end of an alkali solution return main pipe, and the second end of the alkali solution return main pipe is connected to the input port of each electrolyzer. The controller is connected to each electrolyzer, each variable-frequency circulation pump, and the pressure transmitter. The pressure transmitter is disposed on the alkali solution return main pipe between the at least one electrolyzer and the at least one variable-frequency circulation pump. The controller is configured to determine a target variable-frequency circulation pump from the at least one variable-frequency circulation pump based on the number of operating electrolyzers, and control the speed of the target variable-frequency circulation pump based on pressure information collected by the pressure transmitter to maintain a constant pressure in the alkali solution return main pipe. This ensures that the electrolyzers input alkali solution at a constant pressure, making alkali solution flow regulation in the electrolyzers more stable and accurate, and reducing the impact of alkali solution on the pumps caused by load fluctuations.

[0125] FIG7 is a flow chart of a method for preparing hydrogen according to an exemplary embodiment. The hydrogen preparation system includes: a controller, at least one electrolytic cell, at least one variable frequency circulation pump, a gas-liquid separation device, and a pressure transmitter. The output end of the gas-liquid separation device is respectively connected to the input end of each variable frequency circulation pump, the output end of each variable frequency circulation pump is respectively connected to the first end of the alkali liquid return main pipe, the second end of the alkali liquid return main pipe is respectively connected to the input port of each electrolytic cell, and the controller is respectively connected to each electrolytic cell, each variable frequency circulation pump, and the pressure transmitter. The pressure transmitter is arranged on the alkali liquid return main pipe between at least one electrolytic cell and at least one variable frequency circulation pump. As shown in FIG7 , the method applied to the hydrogen preparation system includes:

[0126] Step 201, determining a target variable frequency circulation pump from at least one variable frequency circulation pump according to the number of operating electrolytic cells;

[0127] Step 202: Control the rotation speed of the target variable frequency circulation pump according to the pressure information collected by the pressure transmitter, wherein the pressure information indicates the pressure of the alkali liquid return main pipe between the electrolytic cell and the gas-liquid separation device.

[0128] In step 202 , the rotation speed of the target variable frequency circulation pump is controlled so that the pressure of the alkali solution return main pipe is maintained at a preset pressure.

[0129] The hydrogen production system disclosed herein includes a controller, at least one electrolyzer, at least one variable-frequency circulation pump, a gas-liquid separation device, and a pressure transmitter. The output end of the gas-liquid separation device is connected to the input end of each variable-frequency circulation pump, the output end of each variable-frequency circulation pump is connected to the first end of an alkali solution return main pipe, and the second end of the alkali solution return main pipe is connected to the input port of each electrolyzer. The controller is connected to each electrolyzer, each variable-frequency circulation pump, and the pressure transmitter. The pressure transmitter is disposed on the alkali solution return main pipe between the at least one electrolyzer and the at least one variable-frequency circulation pump. The controller is configured to determine a target variable-frequency circulation pump from the at least one variable-frequency circulation pump based on the number of operating electrolyzers, and control the speed of the target variable-frequency circulation pump based on pressure information collected by the pressure transmitter to maintain a constant pressure in the alkali solution return main pipe. This ensures that the electrolyzers receive a constant pressure of alkali solution, making alkali solution flow regulation in the electrolyzers more stable and accurate, and reducing the impact of alkali solution on the pumps caused by load fluctuations.

[0130] FIG8 is a flow chart of another method for producing hydrogen according to an exemplary embodiment. As shown in FIG8 , in addition to the above steps 201 and 202, the method further includes:

[0131] Step 203: When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than a first pressure threshold, an alarm message is issued;

[0132] Step 204 : When the pressure information indicates that the pressure of the alkali solution return pipe is greater than a second pressure threshold, the electrolytic cell and the variable frequency circulation pump are controlled to stop running, and the second pressure threshold is greater than the first pressure threshold.

[0133] Through the method of this embodiment, when the pressure of the alkali solution return main pipe increases due to the decrease in the alkali solution demand at the outlet of the variable frequency circulation pump of the hydrogen production system, it indicates that the current operating state is prone to safety accidents. In this case, the electrolytic cell 102 and the variable frequency circulation pump 103 can be controlled to stop operating. Otherwise, the excessively low alkali solution flow rate will also damage the electrolytic cell and the variable frequency circulation pump.

[0134] FIG9 is a flow chart of another method for producing hydrogen according to an exemplary embodiment. As shown in FIG9 , in addition to the above steps 201 and 202, the method further includes:

[0135] Step 205 : when the target variable frequency circulation pumps are operating at rated power and the pressure information indicates that the pressure of the alkali solution return main pipe is less than a preset pressure, increase the number of the target variable frequency circulation pumps.

[0136] The method of this embodiment is applicable to situations where the speed of the target variable-frequency circulation pump has been adjusted to operate at rated power, but the pressure of the alkali solution return main has not yet returned to the preset pressure. In this case, to ensure the normal operation of the variable-frequency circulation pump, it is necessary to increase the number of target variable-frequency circulation pumps.

[0137] In some embodiments, there are multiple electrolytic cells, and the hydrogen production system further includes: multiple alkali liquid flow meters and multiple alkali liquid flow regulating valves, wherein the multiple alkali liquid flow meters and the multiple alkali liquid flow regulating valves are respectively connected to the controller;

[0138] Each electrolytic cell is connected to the alkali liquid return main pipe through an alkali liquid return branch pipe. The first end of each alkali liquid return branch pipe is connected to the input port of the electrolytic cell, and the second end is connected to the second end of the alkali liquid return main pipe. Each alkali liquid return branch pipe is provided with an alkali liquid flow meter and an alkali liquid flow regulating valve.

[0139] FIG10 is a flow chart of another method for producing hydrogen according to an exemplary embodiment. As shown in FIG10 , in addition to the above steps 201 and 202, the method further includes:

[0140] Step 206, obtaining the alkali solution flow rate detected by each alkali solution flow meter;

[0141] Step 207, when the alkali liquid flow rate detected by the target alkali liquid flow meter is not equal to the preset alkali liquid flow rate, controlling the opening of the alkali liquid flow regulating valve corresponding to the target alkali liquid flow meter to adjust the alkali liquid flow rate of the alkali liquid return branch pipe where the target alkali liquid flow meter is located to the preset alkali liquid flow rate.

[0142] It should be noted that steps 206 and 207 may be performed after step 202 is performed, or may be performed synchronously with step 202 .

[0143] In other embodiments, the hydrogen production system further comprises: a plurality of gas-liquid separation components and a plurality of gas purity detection components, wherein each electrolyzer corresponds to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe. Each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe is provided with a gas-liquid separation component and a gas purity detection component;

[0144] The first end of each hydrogen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each oxygen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe.

[0145] FIG11 is a flow chart of another method for producing hydrogen according to an exemplary embodiment. As shown in FIG11 , in addition to the above steps 201 and 202, the method further includes:

[0146] Step 208, obtaining the gas purity detected by each gas purity detection component;

[0147] Step 209, when the gas purity detected by the target gas purity detector does not meet the preset purity conditions, adjust the opening of the alkali solution flow control valve corresponding to the target electrolytic cell corresponding to the target gas purity detector to adjust the alkali solution flow input to the target electrolytic cell until the gas purity meets the preset purity conditions.

[0148] For example, when the target gas purity detector detects that the oxygen concentration in hydrogen is greater than 0.5% or the hydrogen concentration in oxygen is greater than 1.5%, the target electrolytic cell is instructed to reduce the alkali solution flow rate, and the opening of the alkali solution flow regulating valve is gradually reduced until the oxygen concentration in hydrogen and the hydrogen concentration in oxygen meet the requirements.

[0149] In other embodiments, the hydrogen production system further includes: a gas-liquid separation component and a gas purity detection component; each electrolytic cell corresponds to a hydrogen exhaust branch pipe and an oxygen exhaust branch pipe;

[0150] The first end of each hydrogen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each oxygen exhaust branch pipe is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe; the hydrogen exhaust main pipe and the oxygen exhaust main pipe are both provided with a gas-liquid separation component and a gas purity detection component, and each hydrogen exhaust branch pipe and each oxygen exhaust branch pipe are provided with a shut-off valve, and each shut-off valve is respectively connected to the controller.

[0151] FIG12 is a flow chart of another method for producing hydrogen according to an exemplary embodiment. As shown in FIG12 , in addition to the above steps 201 and 202, the method further includes:

[0152] Step 210, opening each shut-off valve in sequence to allow the gas purity detection assembly to detect the gas purity of the gas output from each electrolytic cell in sequence;

[0153] Step 211, when it is detected that the gas purity does not meet the preset purity condition, adjust the opening of the alkali solution flow control valve corresponding to the target electrolytic cell to adjust the alkali solution flow input to the target electrolytic cell until the gas purity meets the preset purity condition. The target electrolytic cell is an electrolytic cell whose gas purity of the output gas does not meet the preset purity condition.

[0154] In other embodiments, the preset purity condition includes the following two conditions:

[0155] The hydrogen concentration in the oxygen is less than a first preset concentration threshold; and

[0156] The oxygen concentration in the hydrogen is less than a second preset concentration threshold.

[0157] In step 211, the gas purity does not meet the preset purity condition, including at least one of the following:

[0158] The hydrogen concentration in the oxygen is greater than or equal to a first preset concentration threshold;

[0159] The oxygen concentration in the hydrogen is greater than or equal to a second preset concentration threshold.

[0160] In some other embodiments, an implementation of step 209 or step 211 may be:

[0161] According to the preset flow step, the opening of the alkali solution flow control valve corresponding to the target electrolytic cell is periodically adjusted until the gas purity meets the preset purity condition.

[0162] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0163] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0164] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A hydrogen production system, wherein: The system comprises: a controller, at least one electrolytic cell, at least one variable frequency circulation pump, a gas-liquid separation device and a pressure transmitter; the output end of the gas-liquid separation device is respectively connected to the input end of each variable frequency circulation pump, the output end of each variable frequency circulation pump is respectively connected to the first end of the alkali liquid return main pipe, the second end of the alkali liquid return main pipe is respectively connected to the input port of each electrolytic cell, the controller is respectively connected to each electrolytic cell, each variable frequency circulation pump and the pressure transmitter; the pressure transmitter is arranged on the alkali liquid return main pipe between the at least one electrolytic cell and the at least one variable frequency circulation pump; The controller is used to: Determining a target variable frequency circulation pump from the at least one variable frequency circulation pump according to the number of operations of the electrolytic cell; The rotation speed of the target variable frequency circulation pump is controlled according to the pressure information collected by the pressure transmitter, and the pressure information indicates the pressure of the alkali solution return main pipe.

2. The system according to claim 1, wherein: The controller is also used for: When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than a first pressure threshold, an alarm message is issued; When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than a second pressure threshold, the electrolytic cell and the variable frequency circulation pump are controlled to stop running, and the second pressure threshold is greater than the first pressure threshold.

3. The system according to claim 1, wherein: The controller is also used for: When the target variable frequency circulation pump operates at rated power and the pressure information indicates that the pressure of the alkali solution return main pipe is less than a preset pressure, the number of the target variable frequency circulation pumps is increased.

4. The system according to claim 1, wherein: There are multiple electrolytic cells, and the system further includes: multiple alkali liquid flow meters and multiple alkali liquid flow regulating valves, and the multiple alkali liquid flow meters and the multiple alkali liquid flow regulating valves are respectively connected to the controller; Each of the electrolytic cells is connected to the alkali liquid return main pipe through an alkali liquid return branch pipe, a first end of each of the alkali liquid return branch pipe is connected to the input port of the electrolytic cell, and a second end is connected to the second end of the alkali liquid return main pipe, and each of the alkali liquid return branch pipes is provided with the alkali liquid flowmeter and the alkali liquid flow regulating valve.

5. The system according to claim 4, wherein: The controller is also used for: Obtaining the alkali liquid flow rate detected by each alkali liquid flow meter; When the alkali liquid flow detected by the target alkali liquid flowmeter is not equal to the preset alkali liquid flow rate, the opening of the alkali liquid flow regulating valve corresponding to the target alkali liquid flowmeter is controlled to adjust the alkali liquid flow of the alkali liquid return branch pipe where the target alkali liquid flowmeter is located to the preset alkali liquid flow rate.

6. The system according to claim 4, wherein: The system further comprises: a plurality of gas-liquid separation components and a plurality of gas purity detection components, each of the electrolyzers corresponds to a hydrogen discharge branch pipe and an oxygen discharge branch pipe; each of the hydrogen discharge branch pipes and each of the oxygen discharge branch pipes is provided with the gas-liquid separation component and the gas purity detection component; The first end of each of the hydrogen exhaust branch pipes is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each of the oxygen exhaust branch pipes is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe; The controller is also used for: Obtaining the gas purity detected by each of the gas purity detection components; When the gas purity detected by the target gas purity detector does not meet the preset purity condition, the opening of the alkali solution flow control valve corresponding to the target electrolytic cell is adjusted to adjust the input of the target electrolytic cell. The alkali solution flow rate of the electrolytic cell is adjusted until the gas purity meets the preset purity condition, and the target electrolytic cell is the electrolytic cell corresponding to the target gas purity detector.

7. The system according to claim 4, wherein: The system further comprises: a gas-liquid separation component and a gas purity detection component; each of the electrolyzers corresponds to a hydrogen discharge branch pipe and an oxygen discharge branch pipe; The first end of each of the hydrogen exhaust branch pipes is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each of the oxygen exhaust branch pipes is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe; The hydrogen exhaust main pipe and the oxygen exhaust main pipe are both provided with the gas-liquid separation component and the gas purity detection component, and each of the hydrogen exhaust branch pipes and each of the oxygen exhaust branch pipes is provided with a cut-off valve, and each of the cut-off valves is respectively connected to the controller; The controller is also used for: Opening each of the cut-off valves in sequence, so that the gas purity detection component detects the gas purity of each of the electrolytic cell output gases in sequence; When it is detected that the gas purity does not meet the preset purity conditions, the opening of the alkali solution flow regulating valve corresponding to the target electrolytic cell is adjusted to adjust the alkali solution flow input to the target electrolytic cell until the gas purity meets the preset purity conditions. The target electrolytic cell is an electrolytic cell whose gas purity of the output gas does not meet the preset purity conditions.

8. The system according to claim 6 or 7, wherein: The preset purity conditions include: The hydrogen concentration in the oxygen is less than a first preset concentration threshold; and The oxygen concentration in the hydrogen is less than a second preset concentration threshold.

9. The system according to claim 6 or 7, wherein: The controller is used to: According to the preset flow step, the opening of the alkali solution flow regulating valve corresponding to the target electrolytic cell is periodically adjusted until the gas purity meets the preset purity condition.

10. A method for preparing hydrogen, wherein: The hydrogen preparation system comprises: a controller, at least one electrolytic cell, at least one variable frequency circulation pump, a gas-liquid separation device and a pressure transmitter; the output end of the gas-liquid separation device is respectively connected to the input end of each variable frequency circulation pump, the output end of each variable frequency circulation pump is respectively connected to the first end of the alkali liquid return main pipe, the second end of the alkali liquid return main pipe is respectively connected to the input port of each electrolytic cell, the controller is respectively connected to each electrolytic cell, each variable frequency circulation pump and the pressure transmitter; the pressure transmitter is arranged on the alkali liquid return main pipe between the at least one electrolytic cell and the at least one variable frequency circulation pump; the method is applied to the hydrogen preparation system, and the method comprises: Determining a target variable frequency circulation pump from the at least one variable frequency circulation pump according to the number of operations of the electrolytic cell; The rotation speed of the target variable frequency circulation pump is controlled according to the pressure information collected by the pressure transmitter, wherein the pressure information indicates the pressure of the alkali liquid return main pipe between the electrolytic cell and the gas-liquid separation device.

11. The method according to claim 10, wherein: The method further comprises: When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than a first pressure threshold, an alarm message is issued; When the pressure information indicates that the pressure of the alkali solution return main pipe is greater than a second pressure threshold, the electrolytic cell and the variable frequency circulation pump are controlled to stop running, and the second pressure threshold is greater than the first pressure threshold.

12. The method according to claim 10, wherein: The method further comprises: When the target variable frequency circulation pump operates at rated power and the pressure information indicates that the pressure of the alkali solution return main pipe is less than a preset pressure, the number of the target variable frequency circulation pumps is increased.

13. The method according to claim 10, wherein: There are multiple electrolytic cells, and the system further includes: multiple alkali liquid flow meters and multiple alkali liquid flow regulating valves, and the multiple alkali liquid flow meters and the multiple alkali liquid flow regulating valves are respectively connected to the controller; Each of the electrolytic cells is connected to the alkali liquid return main pipe through an alkali liquid return branch pipe, a first end of each of the alkali liquid return branch pipe is connected to the input port of the electrolytic cell, and a second end is connected to the second end of the alkali liquid return main pipe, and each of the alkali liquid return branch pipes is provided with the alkali liquid flowmeter and the alkali liquid flow regulating valve.

14. The method according to claim 13, wherein: The method further comprises: Obtaining the alkali liquid flow rate detected by each alkali liquid flow meter; When the alkali liquid flow detected by the target alkali liquid flowmeter is not equal to the preset alkali liquid flow rate, the opening of the alkali liquid flow regulating valve corresponding to the target alkali liquid flowmeter is controlled to adjust the alkali liquid flow of the alkali liquid return branch pipe where the target alkali liquid flowmeter is located to the preset alkali liquid flow rate.

15. The method according to claim 13, wherein: The system further comprises: a plurality of gas-liquid separation components and a plurality of gas purity detection components, each of the electrolyzers corresponds to a hydrogen discharge branch pipe and an oxygen discharge branch pipe; each of the hydrogen discharge branch pipes and each of the oxygen discharge branch pipes is provided with the gas-liquid separation component and the gas purity detection component; The first end of each of the hydrogen exhaust branch pipes is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each of the oxygen exhaust branch pipes is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe; The method further comprises: Obtaining the gas purity detected by each of the gas purity detection components; When the gas purity detected by the target gas purity detector does not meet the preset purity conditions, adjust the opening of the alkali solution flow regulating valve corresponding to the target electrolytic cell to adjust the alkali solution flow input to the target electrolytic cell until the gas purity meets the preset purity conditions. The target electrolytic cell is the electrolytic cell corresponding to the target gas purity detector.

16. The method according to claim 13, wherein: The system further comprises: a gas-liquid separation component and a gas purity detection component; each of the electrolyzers corresponds to a hydrogen discharge branch pipe and an oxygen discharge branch pipe; The first end of each of the hydrogen exhaust branch pipes is connected to the output port of the electrolyzer, and the second end is connected to the hydrogen exhaust main pipe; the first end of each of the oxygen exhaust branch pipes is connected to the output port of the electrolyzer, and the second end is connected to the oxygen exhaust main pipe; The hydrogen exhaust main pipe and the oxygen exhaust main pipe are both provided with the gas-liquid separation component and the gas purity detection component, and each of the hydrogen exhaust branch pipes and each of the oxygen exhaust branch pipes is provided with a cut-off valve, and each of the cut-off valves is respectively connected to the controller; The method further comprises: Opening each of the cut-off valves in sequence, so that the gas purity detection component detects the gas purity of each of the electrolytic cell output gases in sequence; When it is detected that the gas purity does not meet the preset purity conditions, the opening of the alkali solution flow regulating valve corresponding to the target electrolytic cell is adjusted to adjust the alkali solution flow input to the target electrolytic cell until the gas purity meets the preset purity conditions. The target electrolytic cell is an electrolytic cell whose gas purity of the output gas does not meet the preset purity conditions.

17. The method according to claim 15 or 16, wherein: The gas purity does not meet the preset purity condition, including at least one of the following: The hydrogen concentration in the oxygen is greater than or equal to a first preset concentration threshold; The oxygen concentration in the hydrogen is greater than or equal to a second preset concentration threshold.

18. The method according to claim 15 or 16, wherein: The adjustment of the opening of the alkali solution flow regulating valve corresponding to the target electrolytic cell includes: According to the preset flow step, the opening of the alkali solution flow regulating valve corresponding to the target electrolytic cell is periodically adjusted.

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