Alkali-containing wastewater zero discharge device and method for water electrolysis-based hydrogen production

Abstract

Disclosed in the present application are an alkali-containing wastewater zero discharge device and method for water electrolysis-based hydrogen production. The device comprises a hydrogen-side water seal device, a hydrogen-side degassing device, a waste alkali collecting tank, a waste alkali pump, an oxygen-side water seal device, and an oxygen-side degassing device. A hydrogen-side liquid phase outlet pipeline of the hydrogen-side degassing device goes downhill and extends inwards to the waste alkali collecting tank; an oxygen-side liquid phase outlet pipeline of the oxygen-side degassing device goes downhill and extends inwards to the waste alkali collecting tank; an exhausting pipeline of the waste alkali collecting tank is communicated with the atmosphere; by means of an inlet pipeline, the waste alkali pump goes downhill and extends inwards to the waste alkali collecting tank, and an outlet of the waste alkali pump is communicated with any one of a water supplementing tank, an alkali blending tank or an alkali transporting tank vehicle. In the present invention, on the premise of ensuring safety and saving investment and an occupied space, alkali-containing wastewater is recycled to serve as a raw material, thereby realizing zero discharge of alkali-containing wastewater; in addition, a centralized alkali-containing wastewater collecting system is designed, so that hydrogen-side and oxygen-side alkali-containing wastewater respectively pass through respective water seal and degassing devices to remove hydrogen and oxygen, and then enter the wastewater collecting system, thereby avoiding formation of explosive gas due to mixing of hydrogen and oxygen.

Description

A zero-discharge device and method for producing hydrogen from alkaline wastewater by water electrolysis Technical Field

[0001] The present invention belongs to the field of water electrolysis hydrogen production, and in particular relates to a zero-discharge device and method for alkaline wastewater in water electrolysis hydrogen production. Background Art

[0002] Currently, the field of hydrogen production by water electrolysis can be divided into four technologies, depending on the type of electrolyte: alkaline water electrolysis (AWE), proton exchange membrane (PEM) water electrolysis, solid oxide electrolysis (SOEC), and anion exchange membrane electrolysis (AEM). Among them, although the efficiency of proton exchange membrane (PEM) water electrolysis has increased to 74-90%, due to the use of relatively expensive materials, the overall cost is relatively high and is currently only used on a small scale; solid oxide electrolysis (SOEC) and anion exchange membrane electrolysis (AEM) are still in the early stages of small-scale commercialization; and alkaline water electrolysis (AWE) technology is the most mature and is most widely used in the field of large-scale energy storage.

[0003] The electrolyte in alkaline electrolyzers typically uses a 30wt% KOH solution with ~0.2wt% V2O5 or potassium dichromate additives. Wastewater is generated during the gas-liquid separation process (gas-liquid separation of alkaline hydrogen and oxygen-containing oxygen), hydrogen drying and purification (dehydration and drying of crude hydrogen), and oxygen drying and purification (dehydration and drying of crude oxygen) of hydrogen electrolysis. The total wastewater discharge contains ~0.03% alkali by weight, along with trace amounts of V2O5 or potassium dichromate additives, significantly exceeding the acceptance criteria of wastewater treatment plants. This often becomes a pain point for wastewater discharge systems and downstream wastewater treatment, and a focus of environmental impact assessments for these projects. Summary of the Invention

[0004] In order to solve the deficiencies in the above-mentioned technical problems, the present invention discloses a zero-discharge device and method for alkaline wastewater for hydrogen production by water electrolysis. Under the premise of ensuring safety and taking into account savings in investment and land occupation, the alkaline wastewater is recovered and used as raw material to achieve zero discharge of alkaline wastewater. At the same time, by designing a centralized alkaline wastewater collection system, the alkaline wastewater on the hydrogen side and the oxygen side are respectively removed from hydrogen and oxygen through their respective water seals and degassing devices before entering the wastewater collection system, thereby avoiding the mixing of hydrogen and oxygen to form explosive gas.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A zero-discharge device for alkaline wastewater for hydrogen production by water electrolysis, comprising a hydrogen side water seal device, a hydrogen side degassing device, a waste alkali collection tank, a waste alkali pump, an oxygen side water seal device, and an oxygen side degassing device, wherein:

[0007] The inlet end of the hydrogen side water seal device is respectively connected to the hydrogen side desalted water pipeline and the hydrogen side alkaline wastewater main pipe, the gas phase outlet of the hydrogen side water seal device is connected to the hydrogen side vent pipeline, the overflow port of the hydrogen side water seal device is connected to the hydrogen side degassing device via the hydrogen side overflow pipeline, and the hydrogen side liquid phase outlet pipeline of the hydrogen side degassing device is downhill and extends inward to the waste alkali collection tank;

[0008] The inlet end of the oxygen side water seal device is respectively connected to the oxygen side desalted water pipeline and the oxygen side alkaline wastewater main pipe, the gas phase outlet of the oxygen side water seal device is connected to the oxygen side vent pipeline, the overflow port of the oxygen side water seal device is connected to the oxygen side degassing device via the oxygen side overflow pipeline, and the oxygen side liquid phase outlet pipeline of the oxygen side degassing device is downhill and extends inward to the waste alkali collection tank;

[0009] The vent line of the waste alkali collecting tank is connected to the atmosphere, the waste alkali pump extends downhill through the inlet pipeline and into the waste alkali collecting tank, and the outlet of the waste alkali pump is connected to any one of the water replenishment tank, the alkali preparation tank or the alkali transport tank truck.

[0010] Preferably, the hydrogen-side alkaline wastewater flows downhill along the hydrogen-side alkaline wastewater main pipe toward the hydrogen-side water seal device.

[0011] Preferably, the oxygen-side alkaline wastewater flows downhill along the oxygen-side alkaline wastewater main pipe toward the oxygen-side water seal device.

[0012] Preferably, a flame arrester is installed on the hydrogen side vent line.

[0013] Preferably, the overflow port of the hydrogen side water seal device is directed downhill toward the hydrogen side degassing device through a hydrogen side overflow pipeline.

[0014] Preferably, the overflow port of the oxygen side water seal device is connected downhill to the oxygen side degassing device through the oxygen side overflow pipeline.

[0015] Preferably, a hydrogen concentration detection alarm and a hydrogen side interlock shut-off valve are provided in the hydrogen side degassing device, and the hydrogen side interlock shut-off valve is used to control the opening and closing of the liquid phase outlet of the hydrogen side degassing device.

[0016] Preferably, an oxygen concentration detection alarm and an oxygen side interlock shut-off valve are provided in the oxygen side degassing device, and the oxygen side interlock shut-off valve is used to control the opening and closing of the liquid phase outlet of the oxygen side degassing device.

[0017] Preferably, a liquid level monitoring device and a liquid level alarm are provided in the waste alkali collection tank.

[0018] Preferably, the outlet of the spent alkali pump is provided with a return line to the spent alkali collection tank.

[0019] A method for discharging alkaline wastewater from a zero-discharge device based on water electrolysis for hydrogen production, the specific steps are as follows:

[0020] Step 1: All hydrogen-containing wastewater and hydrogen-containing waste alkali in water electrolysis hydrogen production are merged into the hydrogen-side alkaline wastewater main pipe, and are passed into the hydrogen-side water seal device through the hydrogen-side alkaline wastewater main pipe; all oxygen-containing wastewater and oxygen-containing waste alkali in water electrolysis hydrogen production are merged into the oxygen-side alkaline wastewater main pipe, and are passed into the oxygen-side water seal device through the oxygen-side alkaline wastewater main pipe;

[0021] Step 2: Continuously replenishing deionized water into the hydrogen side water seal device and the oxygen side water seal device through the hydrogen side deionized water pipeline and the oxygen side deionized water pipeline respectively;

[0022] Step 3: The hydrogen-side alkaline wastewater and the oxygen-side alkaline wastewater overflow through the overflow ports of the hydrogen-side water seal device and the oxygen-side water seal device to the hydrogen-side degassing device and the oxygen-side degassing device respectively;

[0023] Step 4: The hydrogen-side degassing device and the oxygen-side degassing device release and remove the trace hydrogen and oxygen dissolved in the wastewater respectively;

[0024] Step 5: The hydrogen concentration detection alarm in the hydrogen-side degassing device and the oxygen concentration detection alarm in the oxygen-side degassing device respectively monitor and alarm the gas released from the wastewater in real time, and control the opening and closing of the liquid phase outlets of the hydrogen-side degassing device and the oxygen-side degassing device respectively using the hydrogen-side interlock shut-off valve and the oxygen-side interlock shut-off valve according to the monitored gas concentration information;

[0025] Step 6: the alkali-containing wastewater in the hydrogen-side degassing device and the oxygen-side degassing device enters the waste alkali collection tank through the internally extended hydrogen-side liquid phase outlet pipeline and the oxygen-side liquid phase outlet pipeline respectively;

[0026] Step 7: The alkaline wastewater in the waste alkali collection tank is pumped out by the waste alkali pump and sent to the water replenishment tank, alkali preparation tank or alkali transport tank truck.

[0027] Beneficial effects: The present invention discloses a zero-discharge device and method for alkaline wastewater from water electrolysis hydrogen production. Through the reasonable design of the emission recovery device, not only can the alkaline wastewater from water electrolysis hydrogen production be collected and reused to achieve zero discharge of alkaline wastewater, but the alkaline wastewater on the hydrogen side and the oxygen side can also be water-sealed and degassed respectively, so that the hydrogen and oxygen are removed from the alkaline wastewater before entering the wastewater collection system, thereby avoiding the mixing of hydrogen and oxygen to form explosive gas, improving safety performance, and being conducive to meeting environmental protection requirements. In addition, the investment and land occupation are small and the feasibility is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG1 is a schematic diagram of the device structure of this embodiment 1;

[0029] In the figure: 1. Hydrogen side water seal device; 2. Hydrogen side desalted water pipeline; 3. Hydrogen side alkaline wastewater main pipe; 4. Hydrogen side vent pipeline; 5. Flame arrester; 6. Hydrogen side overflow pipeline; 7. Hydrogen side degassing device; 8. Hydrogen side liquid phase outlet pipeline; 9. Oxygen side water seal device; 10. Oxygen side desalted water pipeline; 11. Oxygen side alkaline wastewater main pipe; 12. Oxygen side vent pipeline; 13. Oxygen side overflow pipeline; 14. Oxygen side degassing device; 15. Oxygen side liquid phase outlet pipeline; 16. Waste alkali collection tank; 17. Vent pipeline; 18. Inlet pipeline; 19. Waste alkali pump. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] Example 1

[0032] As shown in FIG1 , a zero-discharge device for alkaline wastewater from water electrolysis hydrogen production includes a hydrogen side water seal device 1, a hydrogen side degassing device 7, a waste alkali collection tank 16, a waste alkali pump 19, an oxygen side water seal device 9, and an oxygen side degassing device 14, wherein:

[0033] The inlet ends of the hydrogen side water seal device 1 are respectively connected with the hydrogen side desalted water pipeline 2 and the hydrogen side alkaline wastewater main pipe 3, the gas phase outlet of the hydrogen side water seal device 1 is connected with the hydrogen side vent pipeline 4, the overflow port of the hydrogen side water seal device 1 is connected with the hydrogen side degassing device 7 via the hydrogen side overflow pipeline 6, and the overflow port of the hydrogen side water seal device 1 is downhill to the hydrogen side degassing device 7 via the hydrogen side overflow pipeline 6, and the hydrogen side liquid phase outlet pipeline 8 of the hydrogen side degassing device 7 is downhill and extends inward to below the liquid level in the waste alkali collection tank 16; in this embodiment 1, the hydrogen side alkaline wastewater flows downhill along the hydrogen side alkaline wastewater main pipe 3 to the hydrogen side water seal device 1, the hydrogen side vent pipeline 4 is installed with a flame arrester 5, and the hydrogen side degassing device 7 is provided with a hydrogen concentration detection alarm and a hydrogen side interlock shut-off valve, which is used to control the switch of the liquid phase outlet of the hydrogen side degassing device.

[0034] The inlet end of the oxygen side water seal device 9 is respectively communicated with the oxygen side desalted water pipeline 10 and the oxygen side alkaline wastewater main pipe 11, the gas phase outlet of the oxygen side water seal device 9 is communicated with the oxygen side vent line 12, the overflow port of the oxygen side water seal device 9 is communicated with the oxygen side degassing device 14 via the oxygen side overflow pipeline 13, and the overflow port of the oxygen side water seal device 9 is downhill to the oxygen side degassing device 14 via the oxygen side overflow pipeline 13, and the oxygen side liquid phase outlet pipeline 15 of the oxygen side degassing device 14 is downhill and extends inward to below the liquid level in the waste alkali collecting tank 16; in the present embodiment 1, the oxygen side alkaline wastewater is downhill to the oxygen side water seal device 9 along the oxygen side alkaline wastewater main pipe 11, and an oxygen concentration detection alarm and an oxygen side interlock shut-off valve are provided in the oxygen side degassing device, and the oxygen side interlock shut-off valve is used to control the switch of the liquid phase outlet of the oxygen side degassing device 14.

[0035] The vent line 17 of the waste alkali collection tank 16 is connected to the atmosphere, and the waste alkali pump 19 (preferably a self-priming pump) is downwardly inclined through the inlet pipeline 18 and extends inward to below the liquid level in the waste alkali collection tank 16. The outlet of the waste alkali pump 19 is connected to any one of the water replenishment tank, alkali preparation tank or alkali transport tank truck. The outlet of the waste alkali pump 19 is provided with a return line to the waste alkali collection tank 16, which can realize the pump withdrawal.

[0036] In this embodiment 1, the hydrogen-side degassing device 7 and the oxygen-side degassing device 14 are both installed indoors, but are also suitable for outdoor installation. The waste alkali collection tank 16 is installed below ground. In the present invention, the installation locations of the hydrogen-side degassing device 7, the oxygen-side degassing device 14, and the waste alkali collection tank 16 can be, but are not limited to, the above-mentioned locations and can be selectively arranged by those skilled in the art according to actual needs.

[0037] In this embodiment 1, the hydrogen side vent line 4, the flame arrester 5 and the oxygen side vent line 12 can be shared by the entire plant. The specific connection can be selectively set by those skilled in the art according to actual needs. It belongs to conventional technology and is not described in detail.

[0038] On the basis of Example 1, a liquid level monitoring device and a liquid level alarm can also be set in the waste alkali collection tank 16, wherein the liquid level monitoring device is used to monitor the liquid level height in the waste alkali collection tank 16 in real time, and the liquid level alarm is used to alarm for liquid levels lower than or higher than a preset value, thereby improving the safety performance of wastewater recovery.

[0039] The specific method for achieving zero discharge of alkaline wastewater from water electrolysis to produce hydrogen using the device of the present invention is as follows:

[0040] Step 1: All hydrogen-containing wastewater and hydrogen-containing waste alkali in water electrolysis hydrogen production are merged into the hydrogen-side alkaline wastewater main pipe 3, and are passed into the hydrogen-side water seal device 1 through the hydrogen-side alkaline wastewater main pipe 3; all oxygen-containing wastewater and oxygen-containing waste alkali in water electrolysis hydrogen production are merged into the oxygen-side alkaline wastewater main pipe 11, and are passed into the oxygen-side water seal device 9 through the oxygen-side alkaline wastewater main pipe 11.

[0041] Step 2: Continuously add deionized water into the hydrogen side water seal device 1 and the oxygen side water seal device 9 through the hydrogen side deionized water pipeline 2 and the oxygen side deionized water pipeline 10 respectively to ensure that the water seal is effective.

[0042] Step 3: The alkaline wastewater on the hydrogen side and the alkaline wastewater on the oxygen side overflow into the hydrogen side degassing device 7 and the oxygen side degassing device 14 through the overflow ports of the hydrogen side water seal device 1 and the oxygen side water seal device 9 respectively.

[0043] Step 4: The hydrogen-side degassing device 7 and the oxygen-side degassing device 14 release the trace hydrogen and oxygen dissolved in the hydrogen-side alkaline wastewater and the oxygen-side alkaline wastewater respectively, and the removed trace hydrogen and oxygen can be directly discharged into the atmosphere.

[0044] Step 5: The hydrogen concentration detection alarm in the hydrogen-side degassing device 7 and the oxygen concentration detection alarm in the oxygen-side degassing device 14 respectively monitor the gas released from the wastewater in real time and sound an alarm, and according to the monitored gas concentration information, the hydrogen-side interlock shut-off valve and the oxygen-side interlock shut-off valve are used to control the switches of the liquid phase outlets of the hydrogen-side degassing device 7 and the oxygen-side degassing device 14 respectively.

[0045] Step 6: the alkali-containing wastewater in the hydrogen-side degassing device 7 and the oxygen-side degassing device 14 enters the waste alkali collection tank through the internally extended hydrogen-side liquid phase outlet pipeline 8 and the oxygen-side liquid phase outlet pipeline 15 respectively.

[0046] Step 7: The alkali-containing wastewater in the waste alkali collection tank 16 is pumped out by the waste alkali pump 19 and sent to the water replenishment tank / alkali preparation tank / alkali transport tank truck to increase operational flexibility.

[0047] In the present invention, the hydrogen side water seal device, the oxygen side water seal device, the fire arrester device and the waste alkali pump are all existing devices, so they are not described in detail.

[0048] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A zero-discharge device for alkaline wastewater from water electrolysis to produce hydrogen, characterized in that: It includes a hydrogen side water seal device, a hydrogen side degassing device, a waste alkali collection tank, a waste alkali pump, an oxygen side water seal device, and an oxygen side degassing device, among which: The inlet end of the hydrogen side water seal device is respectively connected to the hydrogen side desalted water pipeline and the hydrogen side alkaline wastewater main pipe, the gas phase outlet of the hydrogen side water seal device is connected to the hydrogen side vent pipeline, the overflow port of the hydrogen side water seal device is connected to the hydrogen side degassing device via the hydrogen side overflow pipeline, and the hydrogen side liquid phase outlet pipeline of the hydrogen side degassing device is downhill and extends inward to the waste alkali collection tank; The inlet end of the oxygen side water seal device is respectively connected to the oxygen side desalted water pipeline and the oxygen side alkaline wastewater main pipe, the gas phase outlet of the oxygen side water seal device is connected to the oxygen side vent pipeline, the overflow port of the oxygen side water seal device is connected to the oxygen side degassing device via the oxygen side overflow pipeline, and the oxygen side liquid phase outlet pipeline of the oxygen side degassing device is downhill and extends inward to the waste alkali collection tank; The vent line of the waste alkali collecting tank is connected to the atmosphere, the waste alkali pump extends downhill through the inlet pipeline and into the waste alkali collecting tank, and the outlet of the waste alkali pump is connected to any one of the water replenishment tank, the alkali preparation tank or the alkali transport tank truck.

2. The zero-discharge device for alkaline wastewater from water electrolysis hydrogen production according to claim 1, characterized in that: The alkaline wastewater on the hydrogen side flows downhill along the alkaline wastewater main pipe on the hydrogen side to the water seal device on the hydrogen side.

3. The zero-discharge device for alkaline wastewater for producing hydrogen by water electrolysis according to claim 1, characterized in that: The alkaline wastewater on the oxygen side flows downhill along the alkaline wastewater main pipe on the oxygen side to the water seal device on the oxygen side.

4. The zero-discharge device for alkaline wastewater from water electrolysis hydrogen production according to claim 1, characterized in that: A fire arrester is installed on the hydrogen side vent line.

5. The zero-discharge device for alkaline wastewater for producing hydrogen by water electrolysis according to claim 1, characterized in that: The overflow port of the hydrogen side water seal device flows downhill to the hydrogen side degassing device through the hydrogen side overflow pipeline.

6. The zero-discharge device for alkaline wastewater from water electrolysis hydrogen production according to claim 1, characterized in that: The overflow port of the oxygen side water seal device flows downhill to the oxygen side degassing device through the oxygen side overflow pipeline.

7. The zero-discharge device for alkaline wastewater for producing hydrogen by water electrolysis according to claim 1, characterized in that: The hydrogen side degassing device is provided with a hydrogen concentration detection alarm and a hydrogen side interlock shut-off valve, and the hydrogen side interlock shut-off valve is used to control the switch of the liquid phase outlet of the hydrogen side degassing device.

8. The zero-discharge device for alkaline wastewater from water electrolysis hydrogen production according to claim 1, characterized in that: An oxygen concentration detection alarm and an oxygen side interlock shut-off valve are provided in the oxygen side degassing device. The oxygen side interlock shut-off valve is used to control the switch of the liquid phase outlet of the oxygen side degassing device.

9. The zero-discharge device for alkaline wastewater from water electrolysis hydrogen production according to claim 1, characterized in that: A liquid level monitoring device and a liquid level alarm are provided in the waste alkali collection tank.

10. The zero-discharge device for alkaline wastewater for producing hydrogen by water electrolysis according to claim 1, characterized in that: The outlet of the waste alkali pump is provided with a return line to the waste alkali collection tank.

11. A method for discharging alkaline wastewater using a zero-discharge device for producing hydrogen by water electrolysis according to any one of claims 1 to 10, characterized in that: The specific steps are as follows: Step 1: All hydrogen-containing wastewater and hydrogen-containing waste alkali in water electrolysis hydrogen production are merged into the hydrogen-side alkaline wastewater main pipe, and are passed into the hydrogen-side water seal device through the hydrogen-side alkaline wastewater main pipe; all oxygen-containing wastewater and oxygen-containing waste alkali in water electrolysis hydrogen production are merged into the oxygen-side alkaline wastewater main pipe, and are passed into the oxygen-side water seal device through the oxygen-side alkaline wastewater main pipe; Step 2: Continuously replenishing deionized water into the hydrogen side water seal device and the oxygen side water seal device through the hydrogen side deionized water pipeline and the oxygen side deionized water pipeline respectively; Step 3: The hydrogen-side alkaline wastewater and the oxygen-side alkaline wastewater overflow through the overflow ports of the hydrogen-side water seal device and the oxygen-side water seal device to the hydrogen-side degassing device and the oxygen-side degassing device respectively; Step 4: The hydrogen-side degassing device and the oxygen-side degassing device release and remove the trace hydrogen and oxygen dissolved in the wastewater respectively; Step 5: The hydrogen concentration detection alarm in the hydrogen-side degassing device and the oxygen concentration detection alarm in the oxygen-side degassing device respectively monitor and alarm the gas released from the wastewater in real time, and control the opening and closing of the liquid phase outlets of the hydrogen-side degassing device and the oxygen-side degassing device respectively using the hydrogen-side interlock shut-off valve and the oxygen-side interlock shut-off valve according to the monitored gas concentration information; Step 6: the alkali-containing wastewater in the hydrogen-side degassing device and the oxygen-side degassing device enters the waste alkali collection tank through the internally extended hydrogen-side liquid phase outlet pipeline and the oxygen-side liquid phase outlet pipeline respectively; Step 7: The alkaline wastewater in the waste alkali collection tank is pumped out by the waste alkali pump and sent to the water replenishment tank, alkali preparation tank or alkali transport tank truck.

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