Alkaline water electrolysis hydrogen production system and hot start method thereof

Abstract

The invention provides an alkaline water electrolysis hydrogen production system and a hot start method thereof, and relates to the technical field of hydrogen production. In a wind and light coupling hydrogen production project, due to the fact that strong volatility, intermittency and randomness exist in wind and light power generation, time periods with low wind and light output and even no wind and light occur frequently, part of or all hydrogen production systems must be shut down in the time periods, and hot standby, namely heat preservation and pressure preservation, needs to be made after shut down, so that hot start can be conducted immediately, and a working state can be started quickly. The alkaline electrolytic water hydrogen production system is widely applied to engineering as the most mature and low-price hydrogen production system at present. The problem that the peak value of hydrogen impurities in oxygen exceeds a safety limit value easily occurs after the alkaline electrolytic water hydrogen production system is started after hot standby. According to the alkaline water electrolysis hydrogen production system with the buffer tank and the operation method for alternately carrying out liquid-phase nitrogen charging and alkali liquor circulation in the buffer tank before hot start, the safety problem that hydrogen impurities in oxygen exceed the limit after hot start can be effectively avoided on the premise that rapid hot start is guaranteed.

Description

Technical Field

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

[0002] Wind and solar power generation coupled with hydrogen production projects is currently the main form of development of hydrogen energy demonstration projects on the power generation side, and is expected to be the main way to produce green hydrogen in the future.

[0003] In large-scale projects of wind and solar power generation coupled with hydrogen production, alkaline water electrolysis has been the most widely used due to its mature technology and low cost. Due to the strong volatility, intermittency and randomness of wind and solar power generation, there are often periods of low or even no wind and solar power output. During these periods, part or all of the hydrogen production system must be shut down, and hot standby, that is, heat preservation and pressure maintenance, must be done after shutdown so that it can be immediately hot-started and quickly enter the working state.

[0004] After the hot start of the alkaline water electrolysis hydrogen production system, the peak of hydrogen impurities in oxygen is prone to exceed the safety limit. Therefore, frequent hot starts are one of the most important safety issues that need to be paid attention to in the wind-solar power generation coupled alkaline water electrolysis hydrogen production project. The main source of the peak of hydrogen impurities in oxygen after the hot start of the alkaline water electrolysis hydrogen production system is that the hydrogen in the alkali solution enters the gas phase from the liquid phase along with the newly generated gas during the hot start phase. Summary of the invention

[0005] The purpose of the present invention includes providing an alkaline water electrolysis hydrogen production system and a hot start method thereof, which can effectively avoid the safety problem of excessive hydrogen impurities in oxygen after hot start while ensuring rapid hot start.

[0006] The embodiments of the present invention can be implemented as follows:

[0007] In a first aspect, the present invention provides an alkaline water electrolysis hydrogen production system, the alkaline water electrolysis hydrogen production system comprising an electrolyzer, a hydrogen side gas-liquid separator, an oxygen side gas-liquid separator, a buffer tank, an alkali liquid circulation pump, an alkali liquid cooler, an alkali liquid flow meter, a hydrogen side alkali liquid scrubber, an oxygen side alkali liquid scrubber, a hydrogen cooler and an oxygen cooler;

[0008] The hydrogen and alkali liquid two-phase flow outlet of the electrolyzer is connected to the hydrogen and alkali liquid two-phase flow inlet of the hydrogen-side gas-liquid separator through a pipeline, and the oxygen and alkali liquid two-phase flow outlet of the electrolyzer is connected to the oxygen and alkali liquid two-phase flow inlet of the oxygen-side gas-liquid separator through a pipeline;

[0009] The alkali liquid outlets of the hydrogen-side gas-liquid separator and the oxygen-side gas-liquid separator are connected to the alkali liquid inlet of the buffer tank through pipelines;

[0010] The liquid phase outlet of the hydrogen side alkali liquid scrubber is connected to the hydrogen side gas-liquid separator, and the liquid phase outlet of the oxygen side alkali liquid scrubber is connected to the oxygen side gas-liquid separator;

[0011] The alkali liquid outlet of the buffer tank is connected to the alkali liquid inlet of the electrolytic cell through a pipeline branch, and an alkali liquid circulation pump, an alkali liquid cooler and an alkali liquid flow meter are respectively arranged on the pipeline branch along the alkali liquid flow direction;

[0012] The gas phase outlet of the hydrogen side gas-liquid separator, the hydrogen side alkali liquid scrubber and the hydrogen cooler are connected in sequence, and the gas phase outlet of the oxygen side gas-liquid separator, the oxygen side alkali liquid scrubber and the oxygen cooler are connected in sequence.

[0013] In an optional embodiment, a plurality of electrolytic cells are arranged in parallel with each other via a liquid path.

[0014] In an optional embodiment, the alkali solution outlet of the buffer tank is connected to the alkali solution inlets of multiple electrolytic cells through multiple parallel pipeline branches, and each pipeline branch is provided with a alkali solution circulation pump, a alkali solution cooler and an alkali solution flow meter along the alkali solution flow direction.

[0015] In an optional embodiment, the buffer tank is provided with a liquid nitrogen inlet pipeline and a nitrogen outlet pipeline, and the liquid nitrogen inlet pipeline is provided with a regulating valve, a pressure measuring device and a check valve in sequence.

[0016] In an optional embodiment, the regulating valve on the nitrogen outlet pipeline and the gas phase pressure measurement and monitoring device on the buffer tank constitute an automatic control loop for the gas phase pressure of the buffer tank, and the automatic control loop is used to automatically adjust the opening of the regulating valve on the nitrogen outlet pipeline according to the set buffer tank pressure control target value.

[0017] In an optional embodiment, there are multiple liquid nitrogen inlet pipelines and they are arranged at the bottom of the buffer tank to ensure that the nitrogen bubbles are evenly dispersed in the entire liquid phase of the buffer tank when the liquid phase is filled with nitrogen.

[0018] In an optional embodiment, the pressure of the nitrogen source for filling the liquid phase of the buffer tank with nitrogen is at least 0.4 MPa higher than the rated pressure of the alkaline water electrolysis hydrogen production system.

[0019] In a second aspect, the present invention provides a hot start method for the alkaline water electrolysis hydrogen production system of the aforementioned embodiment, the hot start method comprising:

[0020] S1: After setting the pressure control target value of the buffer tank to the actual value of the gas phase pressure of the current buffer tank, the regulating valve on the nitrogen outlet pipeline of the buffer tank is put into automatic mode;

[0021] S2: After opening the nitrogen gas source of the liquid nitrogen inlet pipeline of the buffer tank, gradually increase the opening of the regulating valve on the liquid nitrogen inlet pipeline from 0 until the pressure measured by the pressure measuring device on the liquid nitrogen inlet pipeline is higher than the gas phase pressure measurement value of the buffer tank by a preset pressure value, and stop adjusting the opening of the regulating valve on the liquid nitrogen inlet pipeline;

[0022] S3: After maintaining the first preset time of liquid nitrogen filling, gradually reduce the opening of the regulating valve on the liquid nitrogen inlet pipeline to 0;

[0023] S4: After waiting for a second preset time, turn on the alkali solution circulation pump;

[0024] S5: When the accumulated flow rate measured by the alkali solution flow meter is greater than or equal to the liquid volume in the buffer tank, the alkali solution circulation pump is immediately turned off;

[0025] S6: repeat steps S2-S5 N times, wherein N=ceil (volume of alkali solution in the alkaline water electrolysis hydrogen production system / volume of alkali solution in the buffer tank), and ceil represents rounding up;

[0026] S7: Turn on the alkali solution circulation pump, set the current of the electrolytic cell to the rated current or the current value required by the user, and complete the hot start.

[0027] In an optional implementation, the preset pressure value is 0.2 MPa.

[0028] In an optional implementation, the first preset duration is 1-2 minutes; the second preset duration is 1-2 minutes.

[0029] The alkaline water electrolysis hydrogen production system and hot start method provided by the embodiments of the present invention have the following beneficial effects:

[0030] 1. The alkaline water electrolysis hydrogen production system is equipped with a buffer tank, and the liquid nitrogen filling and alkali solution circulation in the buffer tank are controlled to be performed alternately before hot start. The hydrogen in the alkali solution can be effectively cleared in a short time before hot start, avoiding the safety problem of excessive hydrogen impurities in oxygen after hot start. At the same time, the nitrogen used for purging can be prevented from entering the product gas (oxygen and hydrogen), ensuring that the purity of the product gas can meet the downstream requirements at the initial stage of hot start;

[0031] 2. The alkaline water electrolysis hydrogen production system provided in the embodiment of the present invention has less additional equipment than the traditional design, and thus can significantly increase the safety of the entire system operation with less increase in fixed investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A schematic diagram of the composition of an alkaline water electrolysis hydrogen production system provided in an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of another alkaline water electrolysis hydrogen production system provided in an embodiment of the present invention;

[0035] Figure 3 A flow chart of a hot start method for an alkaline water electrolysis hydrogen production system provided in an embodiment of the present invention.

[0036] Icons: 1-electrolyzer; 2-gas-liquid separator on hydrogen side; 3-gas-liquid separator on oxygen side; 4-buffer tank; 5-alkali solution circulation pump; 6-alkali solution cooler; 7-alkali solution flowmeter; 8-alkali solution scrubber on hydrogen side; 9-alkali solution scrubber on oxygen side; 10-hydrogen cooler; 11-oxygen cooler. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0038] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0040] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0041] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0042] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0043] Please refer to Figure 1 The present embodiment provides an alkaline water electrolysis hydrogen production system, which includes an electrolytic cell 1, a hydrogen side gas-liquid separator 2, an oxygen side gas-liquid separator 3, a buffer tank 4, an alkali liquid circulation pump 5, an alkali liquid cooler 6, an alkali liquid flowmeter 7, a hydrogen side alkali liquid scrubber 8, an oxygen side alkali liquid scrubber 9, a hydrogen cooler 10 and an oxygen cooler 11.

[0044] Specifically, the hydrogen and alkali liquid two-phase flow outlet of the electrolyzer 1 is connected to the hydrogen and alkali liquid two-phase flow inlet of the hydrogen side gas-liquid separator 2 through a pipeline, and the oxygen and alkali liquid two-phase flow outlet of the electrolyzer 1 is connected to the oxygen and alkali liquid two-phase flow inlet of the oxygen side gas-liquid separator 3 through a pipeline.

[0045] The alkali liquid outlets of the hydrogen side gas-liquid separator 2 and the oxygen side gas-liquid separator 3 are connected to the alkali liquid inlet of the buffer tank 4 through pipelines. The liquid phase outlet of the hydrogen side alkali liquid scrubber 8 is connected to the hydrogen side gas-liquid separator 2, and the liquid phase outlet of the oxygen side alkali liquid scrubber 9 is connected to the oxygen side gas-liquid separator 3.

[0046] The alkali solution outlet of the buffer tank 4 is connected to the alkali solution inlet of the electrolytic cell 1 through a pipeline branch, and an alkali solution circulation pump 5, an alkali solution cooler 6 and an alkali solution flow meter 7 are respectively arranged on the pipeline branch along the alkali solution flow direction.

[0047] The gas phase outlet of the hydrogen side gas-liquid separator 2, the hydrogen side alkali liquid scrubber 8 and the hydrogen cooler 10 are connected in sequence, and the gas phase outlet of the oxygen side gas-liquid separator 3, the oxygen side alkali liquid scrubber 9 and the oxygen cooler 11 are connected in sequence.

[0048] The buffer tank 4 is provided with a liquid nitrogen inlet pipeline and a nitrogen outlet pipeline, and a regulating valve, a pressure measuring device and a check valve are sequentially provided on the liquid nitrogen inlet pipeline. The regulating valve on the nitrogen outlet pipeline and the pressure measuring and monitoring device of the gas phase on the buffer tank 4 constitute an automatic control loop for the gas phase pressure of the buffer tank 4, and the automatic control loop is used to automatically adjust the opening of the regulating valve on the nitrogen outlet pipeline according to the set pressure control target value of the buffer tank 4. Among them, there are multiple liquid nitrogen inlet pipelines and they are arranged at the bottom of the buffer tank 4 to ensure that the nitrogen bubbles are evenly dispersed in the entire liquid phase of the buffer tank 4 when the liquid phase is filled with nitrogen.

[0049] The nitrogen source pressure for filling the buffer tank 4 with liquid phase nitrogen is at least 0.4 MPa higher than the rated pressure of the alkaline water electrolysis hydrogen production system. In this embodiment, the rated pressure of the alkaline water electrolysis hydrogen production system is 1.6 MPa, and the nitrogen source pressure for filling the buffer tank 4 with liquid phase nitrogen is at least 2 MPa.

[0050] Please refer to Figure 2The alkaline water electrolysis hydrogen production system provided in this embodiment can also be configured by connecting multiple electrolyzers 1 in parallel through a liquid path. The alkali liquid outlet of the buffer tank 4 is connected to the alkali liquid inlets of the multiple electrolyzers 1 through multiple parallel pipeline branches, and each pipeline branch is respectively provided with an alkali liquid circulation pump 5, an alkali liquid cooler 6 and an alkali liquid flow meter 7 along the alkali liquid flow direction.

[0051] Please refer to Figure 3 This embodiment also provides a hot start method for an alkaline water electrolysis hydrogen production system, the hot start method comprising the following steps:

[0052] S1: After setting the pressure control target value of the buffer tank 4 to the actual value of the gas phase pressure of the current buffer tank 4, the regulating valve on the nitrogen outlet pipeline of the buffer tank 4 is put into automatic mode.

[0053] S2: After opening the nitrogen gas source of the liquid nitrogen inlet pipeline of the buffer tank 4, gradually increase the opening of the regulating valve on the liquid nitrogen inlet pipeline from 0 until the pressure measured by the pressure measuring device on the liquid nitrogen inlet pipeline is higher than the gas phase pressure measurement value of the buffer tank 4 by a preset pressure value, and stop adjusting the opening of the regulating valve on the liquid nitrogen inlet pipeline. The preset pressure value may be 0.2 MPa.

[0054] S3: After maintaining the liquid phase nitrogen filling for a first preset time, gradually reduce the opening of the regulating valve on the liquid nitrogen inlet pipeline to 0. The first preset time may be 1-2 minutes.

[0055] S4: After waiting for a second preset time, turn on the alkali solution circulation pump 5. The second preset time may be 1-2 minutes.

[0056] S5: When the accumulated flow rate measured by the alkali solution flow meter 7 is greater than or equal to the volume of the liquid phase in the buffer tank 4, the alkali solution circulation pump 5 is immediately turned off. The volume of the liquid phase in the buffer tank 4 can be 5m 3 .

[0057] S6: Repeat steps S2-S5 N times, wherein N=ceil (volume of alkali solution in the alkaline water electrolysis hydrogen production system / volume of alkali solution in the buffer tank 4), ceil represents rounding up. The volume of alkali solution in the alkaline water electrolysis hydrogen production system can be 25m 3 ,N=ceil(25m 3 / 5m 3 )=5.

[0058] S7: Turn on the alkali solution circulation pump 5, set the current of the electrolytic cell 1 to the rated current or the current value required by the user, and complete the hot start.

[0059] The alkaline water electrolysis hydrogen production system and hot start method provided by the embodiments of the present invention have the following beneficial effects:

[0060] 1. The alkaline water electrolysis hydrogen production system is equipped with a buffer tank 4, and before hot start, the liquid nitrogen filling and alkali solution circulation in the buffer tank 4 are controlled to be performed alternately, so that the hydrogen in the alkali solution can be effectively cleared in a short time before hot start, avoiding the safety problem of excessive hydrogen impurities in oxygen after hot start. At the same time, the nitrogen used for purging can be prevented from entering the product gas (oxygen and hydrogen), ensuring that the purity of the product gas can meet the downstream requirements at the initial stage of hot start;

[0061] 2. The alkaline water electrolysis hydrogen production system provided in the embodiment of the present invention has less additional equipment than the traditional design, and thus can significantly increase the safety of the entire system operation with less increase in fixed investment.

[0062] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An alkaline water electrolysis hydrogen production system, characterized in that: The alkaline water electrolysis hydrogen production system comprises an electrolyzer (1), a hydrogen-side gas-liquid separator (2), an oxygen-side gas-liquid separator (3), a buffer tank (4), an alkali liquid circulation pump (5), an alkali liquid cooler (6), an alkali liquid flow meter (7), a hydrogen-side alkali liquid scrubber (8), an oxygen-side alkali liquid scrubber (9), a hydrogen cooler (10) and an oxygen cooler (11); The hydrogen and alkali liquid two-phase flow outlet of the electrolytic cell (1) is connected to the hydrogen and alkali liquid two-phase flow inlet of the hydrogen-side gas-liquid separator (2) through a pipeline, and the oxygen and alkali liquid two-phase flow outlet of the electrolytic cell (1) is connected to the oxygen and alkali liquid two-phase flow inlet of the oxygen-side gas-liquid separator (3) through a pipeline; The alkali liquid outlets of the hydrogen side gas-liquid separator (2) and the oxygen side gas-liquid separator (3) are connected to the alkali liquid inlet of the buffer tank (4) through pipelines; The liquid phase outlet of the hydrogen side alkali liquid scrubber (8) is connected to the hydrogen side gas-liquid separator (2), and the liquid phase outlet of the oxygen side alkali liquid scrubber (9) is connected to the oxygen side gas-liquid separator (3); The alkali liquid outlet of the buffer tank (4) is connected to the alkali liquid inlet of the electrolytic cell (1) through a pipeline branch, and the alkali liquid circulation pump (5), the alkali liquid cooler (6) and the alkali liquid flow meter (7) are respectively arranged on the pipeline branch along the alkali liquid flow direction; The gas phase outlet of the hydrogen side gas-liquid separator (2), the hydrogen side alkali liquid scrubber (8) and the hydrogen cooler (10) are connected in sequence, and the gas phase outlet of the oxygen side gas-liquid separator (3), the oxygen side alkali liquid scrubber (9) and the oxygen cooler (11) are connected in sequence.

2. The alkaline water electrolysis hydrogen production system according to claim 1, characterized in that: The plurality of electrolytic cells (1) are arranged in parallel with each other via a liquid path.

3. The alkaline water electrolysis hydrogen production system according to claim 2, characterized in that: The alkali solution outlet of the buffer tank (4) is connected to the alkali solution inlets of the plurality of electrolytic cells (1) via a plurality of parallel pipeline branches, and each of the pipeline branches is provided with the alkali solution circulation pump (5), the alkali solution cooler (6) and the alkali solution flow meter (7) along the alkali solution flow direction.

4. The alkaline water electrolysis hydrogen production system according to claim 1, characterized in that: The buffer tank (4) is provided with a liquid nitrogen inlet pipeline and a nitrogen outlet pipeline, and the liquid nitrogen inlet pipeline is provided with a regulating valve, a pressure measuring device and a check valve in sequence.

5. The alkaline water electrolysis hydrogen production system according to claim 4, characterized in that: The regulating valve on the nitrogen outlet pipeline and the gas phase pressure measurement and monitoring device on the buffer tank (4) form an automatic control loop for the gas phase pressure of the buffer tank (4), and the automatic control loop is used to automatically adjust the opening of the regulating valve on the nitrogen outlet pipeline according to a set buffer tank (4) pressure control target value.

6. The alkaline water electrolysis hydrogen production system according to claim 5, characterized in that: There are a plurality of liquid nitrogen inlet pipelines arranged at the bottom of the buffer tank (4) to ensure that nitrogen bubbles are evenly dispersed into the entire liquid phase of the buffer tank (4) when nitrogen is charged into the liquid phase.

7. The alkaline water electrolysis hydrogen production system according to claim 6, characterized in that: The pressure of the nitrogen gas source for filling the liquid phase of the buffer tank (4) with nitrogen is at least 0.4 MPa higher than the rated pressure of the alkaline water electrolysis hydrogen production system.

8. A hot start method for an alkaline water electrolysis hydrogen production system according to claim 1, characterized in that: The hot start method comprises: S1: after setting the pressure control target value of the buffer tank (4) to the actual value of the gas phase pressure of the buffer tank (4), the regulating valve on the nitrogen outlet pipeline of the buffer tank (4) is put into automatic mode; S2: after opening the nitrogen gas source of the liquid nitrogen inlet pipeline of the buffer tank (4), gradually increasing the opening of the regulating valve on the liquid nitrogen inlet pipeline from 0 until the pressure measured by the pressure measuring device on the liquid nitrogen inlet pipeline is higher than the gas phase pressure measurement value of the buffer tank (4) by a preset pressure value, and then stopping adjusting the opening of the regulating valve on the liquid nitrogen inlet pipeline; S3: After maintaining the liquid phase nitrogen filling for a first preset time, gradually reducing the opening of the regulating valve on the liquid nitrogen inlet pipeline to 0; S4: After waiting for a second preset time, turn on the alkali solution circulation pump (5); S5: When the accumulated flow rate measured by the alkali solution flow meter (7) is greater than or equal to the volume of the liquid phase in the buffer tank (4), the alkali solution circulation pump (5) is immediately turned off; S6: repeat steps S2-S5 N times, wherein N=ceil (volume of alkali solution in the alkaline water electrolysis hydrogen production system / volume of alkali solution in the buffer tank), and ceil represents rounding up; S7: Turn on the alkali solution circulation pump (5), set the current of the electrolytic cell (1) to the rated current or the current value required by the user, and complete the hot start.

9. The hot start method of the alkaline water electrolysis hydrogen production system according to claim 8, characterized in that: The preset pressure value is 0.2Mpa.

10. The hot start method of the alkaline water electrolysis hydrogen production system according to claim 8, characterized in that: The first preset time length is 1-2 minutes; the second preset time length is 1-2 minutes.

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