A hydrogen content control system and method for hydrogen content in oxygen under low load state of an alkaline electrolytic water hydrogen production system

Abstract

This invention discloses a control system and method for controlling the hydrogen content in oxygen under low-load conditions in an alkaline water electrolysis hydrogen production system. The system includes an electrolyzer, a hydrogen separator, an oxygen separator, an alkaline cooler, and an alkaline circulation pump. The electrolyzer is connected to both the hydrogen and oxygen separators. The alkaline cooler is connected to the electrolyzer via the alkaline circulation pump. A PLC control program controls the alkaline circulation pump to control the alkaline flow rate. As the electrolyzer load decreases, the alkaline circulation rate increases accordingly. When the electrolyzer load drops below a low load, the alkaline circulation rate is adjusted synchronously, with the two rates tracking and adjusting in a proportional relationship to ensure that the hydrogen content in oxygen remains within a safe allowable range. When the electrolyzer load fluctuates, the controlled alkaline circulation rate changes accordingly.

Description

Technical Field

[0001] This invention belongs to the field of water electrolysis technology, specifically relating to a control system and method for controlling the hydrogen content in oxygen under low load conditions in an alkaline water electrolysis hydrogen production system. Background Technology

[0002] Gas purity is an important indicator of alkaline water electrolysis. The hydrogen produced during the operation of the hydrogen production system is usually higher than 99.9 vol.% (without additional purification), and the oxygen produced is usually required to be higher than 98.5 vol.%.

[0003] Because these two product gases can form an explosive mixture within a range of approximately 4-96 vol.%, the technical safety limit for emergency shutdown of the entire electrolyzer system is 1.5 vol.%. Therefore, during the operation of the entire hydrogen production system, the hydrogen content in the product gas (oxygen) must be below this limit to ensure continuous operation and production. In the alkaline water electrolysis hydrogen production system, the gas purity increases with increasing current density. However, at lower current densities, the oxygen content produced is lower, causing the hydrogen content in the oxygen produced by alkaline water hydrogen production systems operating at low loads to exceed the required technical safety limit of 1.5 vol.%. Summary of the Invention

[0004] The purpose of this invention is to provide a method for controlling hydrogen in oxygen under low-load operation of an alkaline water electrolysis hydrogen production system, so as to solve the above-mentioned problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A control system for controlling the hydrogen content in oxygen under low-load conditions in an alkaline water electrolysis hydrogen production system includes an electrolyzer, a hydrogen separator, an oxygen separator, an alkaline cooler, and an alkaline circulating pump.

[0007] The electrolytic cell is connected to a hydrogen separator and an oxygen separator, respectively. Both the hydrogen separator and the oxygen separator are connected to an alkali cooler. The alkali cooler is connected to the electrolytic cell through an alkali circulation pump. The alkali circulation pump is controlled by a PLC control program to control the alkali flow rate.

[0008] Preferably, the alkali circulation pump includes alkali circulation pump A or alkali circulation pump B, which transports the alkali in the alkali cooler to the electrolytic cell.

[0009] Preferably, the hydrogen separator is connected to a hydrogen synthesis tower, the hydrogen synthesis tower is connected to a hydrogen-water cooler, the hydrogen-water cooler is connected to a hydrogen-water separator, the hydrogen-water separator discharges unqualified hydrogen and qualified hydrogen in two separate streams, and the hydrogen-water separator is connected to a hydrogen drainer.

[0010] Preferably, the oxygen separator is connected to an aerobic integrated tower, the oxygen integrated tower is connected to an aerobic water cooler, the oxygen water cooler is connected to an oxygen water separator, the oxygen water separator discharges oxygen, and the oxygen water separator is connected to an aerobic drain.

[0011] A control method for controlling the hydrogen content in oxygen in an alkaline water electrolysis hydrogen production system under low load conditions, characterized in that the flow rate of the alkaline solution circulation pump increases when the operating load of the electrolyzer decreases.

[0012] Preferably, a low-load operating parameter range for the electrolyzer is set, and when the electrolyzer enters the low-load parameter range, the alkaline solution circulation control system in the electrolyzer system is activated to adjust the circulation volume.

[0013] Preferably, the alkaline solution circulation rate of the electrolytic cell system is increased according to the load decrease, and the alkaline solution circulation rate is turned up to the maximum when the electrolytic cell load drops to the minimum.

[0014] Preferably, the low-load operating parameter range of the electrolytic cell is set to 0-50% load.

[0015] Preferably, when the electrolyzer enters the preset low load parameter range, the flow rate is increased by frequency conversion control of the alkali circulation pump, and the alkali circulation volume is adjusted according to the load reduction.

[0016] The technical effects and advantages of this invention are as follows: As the load on the electrolyzer decreases, the system controls the alkaline solution circulation volume to increase accordingly. When the electrolyzer load drops below a low load, the alkaline solution circulation volume is adjusted to synchronize the change in alkaline solution circulation volume with the system. The two are adjusted and controlled in a corresponding proportional relationship to ensure that the hydrogen in oxygen is controlled within the allowable safe range. When the load on the electrolyzer fluctuates, the controlled alkaline solution circulation volume changes accordingly to track the load fluctuations. Attached Figure Description

[0017] The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0018] Figure 1 This is a schematic diagram of the system of the present invention.

[0019] Figure 2 This is a schematic diagram showing the relationship between the alkaline solution circulation volume and the load in this invention. Detailed Implementation

[0020] To better understand the technical content of this invention, specific embodiments are described below in conjunction with the accompanying drawings. Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, which illustrate numerous illustrative embodiments. The embodiments of this disclosure are not necessarily defined to include all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed in this invention are not limited to any particular implementation. Furthermore, some aspects of this invention can be used alone or in any suitable combination with other aspects of this invention.

[0021] like Figure 1 As shown, the present invention provides a control system for the hydrogen content in oxygen under low load conditions in an alkaline water electrolysis hydrogen production system, including an electrolyzer, a hydrogen separator, an oxygen separator, an alkaline cooler, and an alkaline circulating pump.

[0022] The electrolytic cell is connected to a hydrogen separator and an oxygen separator, respectively. Both the hydrogen separator and the oxygen separator are connected to an alkali cooler. The alkali cooler is connected to the electrolytic cell through an alkali circulation pump. The alkali circulation pump is controlled by a PLC control program to control the alkali flow rate.

[0023] The alkali circulation pump includes alkali circulation pump A or alkali circulation pump B, which transports the alkali in the alkali cooler to the electrolytic cell.

[0024] The hydrogen separator is connected to a hydrogen synthesis tower, the hydrogen synthesis tower is connected to a hydrogen-water cooler, the hydrogen-water cooler is connected to a hydrogen-water separator, the hydrogen-water separator discharges unqualified hydrogen and qualified hydrogen in two separate streams, and the hydrogen-water separator is connected to a hydrogen drainer.

[0025] The oxygen separator is connected to the aerobic integrated tower, the oxygen integrated tower is connected to the aerobic water cooler, the oxygen water cooler is connected to the oxygen water separator, the oxygen water separator discharges oxygen, and the oxygen water separator is connected to the aerobic drain.

[0026] To achieve the above objectives, the present invention provides another technical solution as follows:

[0027] A method for controlling hydrogen in oxygen under low-load operation of an alkaline water electrolysis hydrogen production system involves setting a low-load operating parameter range for the electrolyzer, and activating the alkaline solution circulation control system within the electrolyzer system to adjust the circulation rate when the electrolyzer enters the low-load parameter range.

[0028] Preferably, the alkaline solution circulation rate of the electrolytic cell system is increased according to the load decrease, and the alkaline solution circulation rate is turned up to the maximum when the electrolytic cell load drops to the minimum.

[0029] Preferably, the low-load operating parameter range of the electrolytic cell is set to 0-50% load.

[0030] Preferably, when the electrolyzer's operating condition enters a preset low-load parameter range, the flow rate is increased using frequency conversion control of the alkali circulation pump, while the alkali circulation volume is adjusted according to load reduction changes.

[0031] Specifically, the low-load operating parameter range of the electrolytic cell is set to 0-50% load. This low-load operating parameter range is not unique and can be set according to the actual situation of the user.

[0032] Specifically, when the electrolyzer enters the preset low load parameter range, the flow rate is increased by frequency conversion control of the alkali circulation pump, and the alkali circulation volume is adjusted according to the load reduction.

[0033] Working principle: The automatic control system adopts a programmable logic controller (PLC). The system is configured with a Siemens 1500 series-1513 CPU master station + ET200sp slave station, with the PLC acting as the slave station. The entire alkaline water electrolysis hydrogen production system is in automatic mode. The hydrogen and oxygen side valves are automatically opened to maintain a continuous venting state. The hydrogen and oxygen side regulating valves, cooling water regulating valve, rectifier, circulating pump, and makeup water pump are in automatic mode. The alkaline solution inlet regulating valve is in manual mode at 50% opening. The rectifier current gain, current rise target value, and system pressure are set. The circulating pump is selected. Once ready, on-site personnel are notified for inspection. If no problems are found, the one-button start is pressed. If problems occur, the above steps are repeated.

[0034] Once the entire system reaches the set values ​​according to the pre-set parameters, and the pressure, temperature, flow rate, liquid level, oxygen-hydrogen ratio, and hydrogen-oxygen ratio are stable, the system load is reduced accordingly. The inlet flow rate SV is set accordingly. This set value is not unique and can be set according to the user's actual needs. The PV value is detected by the electromagnetic flowmeter, and the actual flow rate is calculated by PID control to obtain a suitable 4-20mA analog quantity. The frequency converter controls the flow rate of the alkali circulation pump, thereby adjusting the alkali flow rate and flow rate, and thus adjusting the voltage and gas purity in the small chamber of the tank. The change in gas purity changes the technical safety threshold of hydrogen peroxide. It can also "stir" the electrolysis reaction area in the electrolytic cell to reduce concentration polarization.

[0035] Then, the flow rate is controlled by a variable frequency pump to change according to the load reduction, ensuring that the parameters remain stable under changing operating conditions.

[0036] At this point, the hydrogen content in the oxygen fluctuates from a steady state to a rated value and then gradually decreases. After reaching a steady state, the load is reduced sequentially to 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, and 5% in the same manner to achieve the final low-load operation target, thereby reaching a simulated trend chart for regulation, which facilitates the control of the technical safety limit of hydrogen peroxide.

[0037] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A control system for hydrogen content in oxygen in a low load state of an alkaline electrolytic water hydrogen production system, characterized by: It includes an electrolytic cell, a hydrogen separator, an oxygen separator, an alkali cooler, and an alkali circulation pump; The electrolytic cell is connected to a hydrogen separator and an oxygen separator, respectively. Both the hydrogen separator and the oxygen separator are connected to an alkali cooler. The alkali cooler is connected to the electrolytic cell via an alkali circulation pump. The alkali circulation pump is controlled by a PLC control program to control the alkali flow rate. When the operating load of the electrolytic cell decreases, the flow rate of the alkali circulation pump increases. The alkali circulation pump includes alkali circulation pump A or alkali circulation pump B, which transports the alkali in the alkali cooler to the electrolytic cell. The hydrogen separator is connected to a hydrogen synthesis tower, the hydrogen synthesis tower is connected to a hydrogen-water cooler, the hydrogen-water cooler is connected to a hydrogen-water separator, the hydrogen-water separator discharges unqualified hydrogen and qualified hydrogen in two separate streams, and the hydrogen-water separator is connected to a hydrogen drainer. The oxygen separator is connected to the aerobic integrated tower, the oxygen integrated tower is connected to the aerobic water cooler, the oxygen water cooler is connected to the oxygen water separator, the oxygen water separator discharges oxygen, and the oxygen water separator is connected to the aerobic drain.

2. The control method of the hydrogen content in oxygen control system of an alkaline water electrolysis hydrogen generation system in a low load state according to claim 1, characterized by, Set the low-load operating parameter range for the electrolyzer. Once the electrolyzer enters the low-load parameter range, activate the alkaline circulation control system in the electrolyzer system to adjust the circulation rate. The alkaline solution circulation rate of the electrolytic cell system is increased according to the load decrease. When the electrolytic cell load drops to its minimum, the alkaline solution circulation rate is increased to its maximum.

3. The control method of the hydrogen content in oxygen control system of an alkaline water electrolysis hydrogen production system at low load according to claim 2, characterized in that: The low-load operating parameter range of the electrolytic cell is set to 0-50% load.

4. The control method of the hydrogen content in oxygen control system of an alkaline water electrolysis hydrogen production system at low load according to claim 2, characterized in that: When the electrolyzer enters the preset low load parameter range, the flow rate is increased by frequency conversion control of the alkali circulation pump, and the alkali circulation volume is adjusted according to the load reduction.

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