A water electrolysis device and method

Abstract

The invention relates to a water electrolysis apparatus and method. The apparatus comprises an electrolysis cell for electrolysis of an alkali solution to produce hydrogen and oxygen; a hydrogen separator for flashing off hydrogen and entrained alkali solution produced by electrolysis; an oxygen separator for flashing off oxygen and entrained alkali solution produced by electrolysis; a hydrogen gradient separator for receiving and flashing off the liquid phase from the hydrogen separator; an oxygen gradient separator for receiving and flashing off the liquid phase from the oxygen separator; and a line for mixing the flashed liquid phases from the hydrogen and oxygen gradient separators and returning to the electrolysis cell, or a line for returning the flashed liquid phases from the hydrogen and oxygen gradient separators separately to the electrolysis cell.

Description

Technical Field

[0001] This invention relates to a water electrolysis apparatus and method. Background Technology

[0002] Peaking China's carbon dioxide emissions before 2030 and achieving carbon neutrality before 2060 is one of China's key tasks for the foreseeable future. Actively exploring new clean energy sources will help accelerate the process of peaking carbon emissions and achieving carbon neutrality, and expedite the optimization of the industrial structure. Hydrogen energy, as a green energy source with abundant reserves, high calorific value, high energy density, and diverse sources, is hailed as the "ultimate energy" of the 21st century.

[0003] Using renewable energy to electrolyze water to produce hydrogen is a new development trend in the hydrogen energy industry. By utilizing wind, solar, and hydropower resources to streamline the hydrogen production process, energy waste can be minimized, the economic efficiency of water electrolysis for hydrogen production can be improved, and the needs of green energy sustainable development can be met.

[0004] The inability of green energy sources such as wind and solar power to provide a continuous and stable power output poses a significant challenge to the operation of medium- and high-pressure water electrolysis units. This is because, when operating under low load or low current density, the hydrogen concentration in the oxygen product gas can rise dramatically to near the lower explosive limit, posing a substantial safety risk to the operation of medium- and high-pressure water electrolysis units. Therefore, how to safely utilize wind and solar energy in medium- and high-pressure water electrolysis units remains a problem to be solved.

[0005] Traditional medium- and high-pressure water electrolysis units typically only have hydrogen and oxygen separators, with operating pressures ranging from 10 to 30 bar. When the load or current density of the water electrolyzer is too low, for example during startup and shutdown or a sudden and significant reduction in power input, the hydrogen content in the crude oxygen product gas will rise sharply. Summary of the Invention

[0006] The purpose of this invention is to provide a water electrolysis device and method that solves the safety problems caused by traditional medium / high pressure water electrolysis devices operating at low current densities, while ensuring that the pressure of hydrogen and oxygen products does not fluctuate in downstream devices. When the water electrolyzer operates under low current density conditions, the alkali solution undergoes multi-gradient pressure operation. Gases dissolved in the alkali solution are discharged from the alkali solution circulation system, reducing the hydrogen content in the oxygen product gas and ensuring that the hydrogen concentration in the oxygen is below the lower explosive limit, thereby achieving safe production of the medium / high pressure water electrolysis device under low current density operation. This significantly expands the operating range of the medium / high pressure water electrolysis device and improves its safety and reliability.

[0007] This invention provides a water electrolysis device, comprising:

[0008] An electrolytic cell is used to electrolyze alkaline solutions to produce hydrogen and oxygen.

[0009] Hydrogen separator, used for hydrogen and entrained alkali solution generated by flash electrolysis;

[0010] An oxygen separator is used to separate the oxygen produced by flash electrolysis from the entrained alkali solution.

[0011] A hydrogen gradient separator is used to receive and flash the liquid phase after flashing in the hydrogen separator;

[0012] An oxygen gradient separator is used to receive and flash the liquid phase after flashing in an oxygen separator; and

[0013] The pipeline that returns the liquid phases after flash evaporation from the hydrogen gradient separator and the oxygen gradient separator to the electrolyzer can be either mixed or returned separately to the electrolyzer.

[0014] The present invention also provides a water electrolysis device, including

[0015] An electrolytic cell is used to electrolyze alkaline solutions to produce hydrogen and oxygen.

[0016] Hydrogen separator, used for hydrogen gas and entrained alkali solution generated by flash electrolysis;

[0017] An oxygen separator is used to separate the oxygen produced by flash electrolysis from the entrained alkali solution.

[0018] A gradient separator is used to receive and flash the liquid phase from the hydrogen separator and the liquid phase from the oxygen separator; and

[0019] The pipeline that returns the liquid phase after flash evaporation in the gradient separator to the electrolyzer.

[0020] The present invention also provides a water electrolysis method, including

[0021] Hydrogen and oxygen are produced by electrolyzing an alkaline solution in an electrolytic cell.

[0022] Hydrogen and entrained alkaline solution produced by flash electrolysis in a hydrogen separator;

[0023] Oxygen and entrained alkali solution produced by flash electrolysis in an oxygen separator;

[0024] The liquid phase after flashing in the hydrogen separator is received and flashed through the hydrogen gradient separator;

[0025] The liquid phase after flashing in the oxygen separator is received and flashed through the oxygen gradient separator; and

[0026] The liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator are mixed and returned to the electrolytic cell, or the liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator are returned to the electrolytic cell separately.

[0027] The present invention also provides a water electrolysis method, including

[0028] Hydrogen and oxygen are produced by electrolyzing an alkaline solution in an electrolytic cell.

[0029] Hydrogen and entrained alkaline solution produced by flash electrolysis in a hydrogen separator;

[0030] Oxygen and entrained alkali solution produced by flash electrolysis in an oxygen separator;

[0031] The gradient separator receives and flashes the liquid phase from the hydrogen separator and the liquid phase from the oxygen separator; and

[0032] The liquid phase after flash evaporation in the gradient separator is returned to the electrolytic cell.

[0033] The system automatically adjusts the operating pressure of the alkali solution based on the load or current density. Dissolved gases in the alkali solution can be discharged from the circulation system, thereby reducing the oxygen content in hydrogen products and the hydrogen content in oxygen products, achieving the goal of safe production.

[0034] This invention employs a gradient pressure process in traditional medium- and high-pressure water electrolysis devices. While ensuring stable operating pressures for the hydrogen and oxygen product gases, it extends the load fluctuation range of the water electrolyzer to 15-100%, while maintaining a hydrogen concentration of less than 2% in the crude oxygen product gas. This significantly improves the safety of wide-range operation of the medium- and high-pressure water electrolyzer and provides a safe technical solution for directly utilizing unstable green energy sources such as wind or solar power as the energy input for water electrolysis devices. Attached Figure Description

[0035] Figure 1 This is a diagram of a water electrolysis apparatus according to one embodiment of the present invention;

[0036] Figure 2 This is a diagram of a water electrolysis apparatus according to another embodiment of the present invention;

[0037] Figure 3 This is a diagram of a water electrolysis apparatus according to another embodiment of the present invention. Detailed Implementation

[0038] In one aspect, the present invention relates to a water electrolysis apparatus, comprising:

[0039] An electrolytic cell is used to electrolyze alkaline solutions to produce hydrogen and oxygen.

[0040] Hydrogen separator, used for hydrogen gas and entrained alkali solution generated by flash electrolysis;

[0041] An oxygen separator is used to separate the oxygen produced by flash electrolysis from the entrained alkali solution.

[0042] A hydrogen gradient separator is used to receive and flash the liquid phase after flashing in the hydrogen separator;

[0043] An oxygen gradient separator is used to receive and flash the liquid phase after flashing in an oxygen separator; and

[0044] The pipeline that returns the liquid phases after flash evaporation from the hydrogen gradient separator and the oxygen gradient separator to the electrolyzer can be either mixed or returned separately to the electrolyzer.

[0045] In one aspect, the water electrolysis apparatus further includes

[0046] Hydrogen scrubber, used to wash away alkaline solution entrained in hydrogen after flash evaporation in a hydrogen separator and to produce crude hydrogen; and / or

[0047] An oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen separator and to produce crude oxygen.

[0048] In one aspect, the water electrolysis apparatus further includes

[0049] Replenish pipelines that supply water consumed in the production of hydrogen and oxygen.

[0050] In one aspect, the water electrolysis apparatus further includes

[0051] A hydrogen purge scrubber is used to wash away the alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen gradient separator and to produce hydrogen purge gas; and / or

[0052] A purge oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen gradient separator and to produce oxygen purge gas.

[0053] In one aspect, the apparatus includes a pipeline that returns the liquid phases from the flash evaporation of the hydrogen gradient separator and the oxygen gradient separator to the electrolyzer, and the pipeline includes a circulation flow regulating valve.

[0054] In one aspect, the apparatus includes lines for returning the liquid phases after flash evaporation from the hydrogen gradient separator and the oxygen gradient separator to the electrolyzer, respectively, and includes a circulation flow regulating valve in the lines for returning the liquid phases after flash evaporation from the hydrogen gradient separator to the electrolyzer and / or in the lines for returning the liquid phases after flash evaporation from the oxygen gradient separator to the electrolyzer.

[0055] In one aspect, the water electrolysis apparatus further includes

[0056] Liquid phase balance tube between the hydrogen gradient separator and the oxygen gradient separator.

[0057] In one aspect, the operating pressure of the electrolytic cell is 10-30 barg.

[0058] In one aspect, the hydrogen separator and oxygen separator operate at a pressure of 10-30 bar.

[0059] In one aspect, the hydrogen gradient separator and the oxygen gradient separator operate at a pressure of 1-30 barA.

[0060] In one aspect, the operating pressure of the hydrogen gradient separator and the oxygen gradient separator is maintained by the gas phase flashed from the hydrogen gradient separator and the oxygen gradient separator, or by the gas phase flashed from the hydrogen separator and the oxygen separator, or by an inert gas. The inert gas is, for example, nitrogen.

[0061] In one aspect, it also includes a circulation pump downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the electrolyzer.

[0062] In one aspect, the system further includes a circulating alkali cooler downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali cooler.

[0063] In one aspect, the present invention relates to a water electrolysis apparatus, comprising:

[0064] An electrolytic cell is used to electrolyze alkaline solutions to produce hydrogen and oxygen.

[0065] Hydrogen separator, used for hydrogen and entrained alkali solution generated by flash electrolysis;

[0066] An oxygen separator is used to separate the oxygen produced by flash electrolysis from the entrained alkali solution.

[0067] A gradient separator is used to receive and flash the liquid phase from the hydrogen separator and the liquid phase from the oxygen separator; and

[0068] The pipeline that returns the liquid phase after flash evaporation in the gradient separator to the electrolyzer.

[0069] In one aspect, the water electrolysis apparatus further includes

[0070] Hydrogen scrubber, used to wash away alkaline solution entrained in hydrogen after flash evaporation in a hydrogen separator and to produce crude hydrogen; and / or

[0071] An oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen separator and to produce crude oxygen.

[0072] In one aspect, the water electrolysis apparatus further includes

[0073] Replenish pipelines that supply water consumed in the production of hydrogen and oxygen.

[0074] In one aspect, the water electrolysis apparatus further includes

[0075] A purge gas scrubber is used to wash away the alkaline solution entrained in the gas after flash evaporation in the gradient separator and to generate purge gas.

[0076] In one aspect, the pipeline that returns the liquid phase after flash evaporation in the gradient separator to the electrolyzer includes a circulation flow regulating valve.

[0077] In one aspect, the operating pressure of the electrolytic cell is 10-30 barg.

[0078] In one aspect, the hydrogen separator and oxygen separator operate at a pressure of 10-30 bar.

[0079] In one aspect, the gradient separator operates at a pressure of 1-5 barA.

[0080] In one aspect, the operating pressure of the gradient separator is maintained by the gas phase flashed from the gradient separator, or by the gas phase flashed from the hydrogen and oxygen separators, or by an inert gas, such as nitrogen.

[0081] In one aspect, a circulating pump is also included downstream of the gradient separator and upstream of the electrolyzer.

[0082] In one aspect, the system also includes a circulating alkali cooler downstream of the gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali cooler.

[0083] In one aspect, the present invention relates to a water electrolysis method, comprising:

[0084] Hydrogen and oxygen are produced by electrolyzing an alkaline solution in an electrolytic cell.

[0085] Hydrogen and entrained alkaline solution produced by flash electrolysis in a hydrogen separator;

[0086] Oxygen and entrained alkali solution produced by flash electrolysis in an oxygen separator;

[0087] The liquid phase after flashing in the hydrogen separator is received and flashed through the hydrogen gradient separator;

[0088] The liquid phase after flashing in the oxygen separator is received and flashed through the oxygen gradient separator; and

[0089] The liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator are mixed and returned to the electrolytic cell, or the liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator are returned to the electrolytic cell separately.

[0090] In one aspect, the water electrolysis method further includes

[0091] The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen separator is washed away by a hydrogen scrubber, producing crude hydrogen; and / or

[0092] The oxygen scrubber removes the alkaline solution entrained in the oxygen after flash evaporation in the oxygen separator and produces crude oxygen.

[0093] In one aspect, the water electrolysis method further includes

[0094] Replenish the water consumed in the production of hydrogen and oxygen.

[0095] In one aspect, the water electrolysis method further includes

[0096] The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen gradient separator is washed away by a hydrogen purge scrubber, and hydrogen purge gas is generated; and / or

[0097] The oxygen is washed away by a purge oxygen scrubber to remove the alkaline solution entrained in the oxygen after flash evaporation in the oxygen gradient separator and to produce oxygen purge gas.

[0098] In one aspect, the water electrolysis method further includes

[0099] The circulation volume of alkali solution is controlled by a circulation flow regulating valve in the pipeline that returns the liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator to the electrolyzer. Specifically, the circulation volume of alkali solution is reduced when the load or current density of the water electrolysis unit decreases.

[0100] In one aspect, the water electrolysis method further includes

[0101] The alkali circulation volume is controlled by a circulation flow regulating valve included in the pipeline that returns the liquid phase after flash evaporation from the hydrogen gradient separator to the electrolyzer and / or in the pipeline that returns the liquid phase after flash evaporation from the oxygen gradient separator to the electrolyzer, wherein the alkali circulation volume is reduced when the load or current density of the water electrolysis unit decreases.

[0102] In one aspect, the water electrolysis method further includes

[0103] The pressure difference between the cathode and anode chambers of the electrolyzer is reduced by using a liquid phase balance tube between the hydrogen gradient separator and the oxygen gradient separator.

[0104] In one aspect, the operating pressure of the electrolytic cell is 10-30 barg.

[0105] In one aspect, the hydrogen separator and oxygen separator operate at a pressure of 10-30 bar.

[0106] In one aspect, the hydrogen gradient separator and the oxygen gradient separator operate at a pressure of 1-30 barA.

[0107] In one aspect, the operating pressure of the hydrogen gradient separator is adjusted according to the liquid level difference between the hydrogen gradient separator and the oxygen gradient separator.

[0108] In one aspect, the operating pressure of the hydrogen gradient separator and / or the oxygen gradient separator is adjusted according to the electrolyzer operating load or current density.

[0109] In one aspect, the operating pressure of the hydrogen gradient separator and the oxygen gradient separator is maintained by the gas phase flashed from the hydrogen gradient separator and the oxygen gradient separator, or by the gas phase flashed from the hydrogen separator and the oxygen separator, or by an inert gas. The inert gas is, for example, nitrogen.

[0110] In one aspect, the water electrolysis method further includes circulating an alkaline solution via a circulation pump downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the electrolyzer.

[0111] In one aspect, the water electrolysis method further includes cooling the alkali solution via a circulating alkali solution cooler downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali solution cooler.

[0112] In one aspect, the present invention relates to a water electrolysis method, comprising:

[0113] Hydrogen and oxygen are produced by electrolyzing an alkaline solution in an electrolytic cell.

[0114] Hydrogen and entrained alkaline solution produced by flash electrolysis in a hydrogen separator;

[0115] Oxygen and entrained alkali solution produced by flash electrolysis in an oxygen separator;

[0116] The gradient separator receives and flashes the liquid phase from the hydrogen separator and the liquid phase from the oxygen separator; and

[0117] The liquid phase after flash evaporation in the gradient separator is returned to the electrolytic cell.

[0118] In one aspect, the water electrolysis method further includes

[0119] The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen separator is washed away by a hydrogen scrubber, producing crude hydrogen; and / or

[0120] The oxygen scrubber removes the alkaline solution entrained in the oxygen after flash evaporation in the oxygen separator and produces crude oxygen.

[0121] In one aspect, the water electrolysis method further includes

[0122] Replenish the water consumed in the production of hydrogen and oxygen.

[0123] In one aspect, the water electrolysis method further includes

[0124] The alkali entrained in the gas after flash evaporation in the gradient separator is washed away by the vent gas scrubber, and vent gas is generated.

[0125] In one aspect, the water electrolysis method further includes

[0126] The amount of alkali solution circulating is controlled by a circulation flow regulating valve included in the pipeline that returns the liquid phase after flash evaporation in the gradient separator to the electrolyzer.

[0127] In one aspect, the operating pressure of the electrolytic cell is 10-30 barg.

[0128] In one aspect, the hydrogen separator and oxygen separator operate at a pressure of 10-30 bar.

[0129] In one aspect, the gradient separator operates at a pressure of 1-5 barA.

[0130] In one aspect, the operating pressure of the gradient separator is adjusted according to the electrolytic cell operating load or current density.

[0131] In one aspect, the operating pressure of the gradient separator is maintained by the gas phase flashed from the gradient separator, or by the gas phase flashed from the hydrogen and oxygen separators, or by an inert gas, such as nitrogen.

[0132] In one aspect, the water electrolysis method further includes circulating an alkaline solution via a circulation pump located downstream of the gradient separator and upstream of the electrolyzer.

[0133] In one aspect, the water electrolysis method further includes cooling the alkali solution via a circulating alkali solution cooler downstream of the gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali solution cooler.

[0134] In one aspect, after the liquid phase enters the gradient separator, the hydrogen and oxygen in the gas phase generated by the flash evaporation of the gradient separator are diluted with an inert gas, such as nitrogen.

[0135] In one aspect, hydrogen gradient separators and oxygen gradient separators are respectively installed in the liquid phase flow paths of the hydrogen separator and oxygen separator. The concentration of dissolved gases in the alkaline solution is reduced by controlling the pressure of the oxygen gradient separator at different rates. Typically, the operating pressure of the hydrogen and oxygen gradient separators can be controlled between 1 and 30 bar. This reduces the hydrogen content in the crude oxygen product gas under extremely low operating loads or low current density conditions, improving the safe operation of the water electrolysis unit over a wide operating range. Because hydrogen separators, oxygen separators, hydrogen gradient separators, and oxygen gradient separators are installed simultaneously, the operating pressures of the hydrogen and oxygen separators remain constant under any operating condition, even at low loads or low current densities. Consequently, the operating pressures of the crude hydrogen and crude oxygen product gases can be maintained stably under any conditions. Water electrolysis units employing gradient pressure technology can operate safely and long-term under low load or low current density conditions. This improves the feasibility and utilization rate of wind and solar energy as energy sources for water electrolysis devices, and also reduces the safety risks caused by the frequent shutdowns of water electrolysis devices due to the instability of wind and solar energy.

[0136] In one aspect, an alkali circulation flow regulating valve is installed on the flow path of the alkali solution returning to the water electrolyzer. When the load or current density of the water electrolyzer decreases, the alkali circulation flow rate is reduced, thereby decreasing the flow of hydrogen and oxygen entering the cathode and anode chambers of the water electrolyzer through the circulating alkali solution. This reduces the hydrogen content in the crude oxygen product gas and improves the safe operation of the water electrolyzer over a wide operating range. The alkali circulation rate can be adjusted according to the temperature difference on the hot side of the alkali circulation cooler. The alkali circulation rate can be adjusted within the load range of 10% to 100%.

[0137] In one aspect, a liquid phase balance tube is installed between the hydrogen gradient separator and the oxygen gradient separator. This avoids excessive pressure difference between the cathode and anode chambers of the water electrolyzer, which could damage the diaphragm and reduce the risk of high hydrogen concentration in the crude oxygen product gas due to diaphragm damage.

[0138] In one aspect, the operating pressures of the hydrogen gradient separator and the oxygen gradient separator can be set according to the operating load or current density of the water electrolyzer, so as to ensure that the operating pressures of the hydrogen gradient separator and the oxygen gradient separator can respond instantly to changes in load or current density.

[0139] Example

[0140] Example 1

[0141] refer to Figure 1The alkali solution is pressurized by the circulating pump P-101 to the required operating pressure of 10-30 barg in electrolytic cell A-101, and then enters the cathode and anode chambers of electrolytic cell A-101, respectively. Under the action of electrical energy and the cathode / anode electrodes, the water in the alkali solution decomposes, producing hydrogen and oxygen in the cathode and anode chambers, respectively. The hydrogen and oxygen produced by decomposition, along with the alkali solution, enter the hydrogen separator V-101 and oxygen separator V-102 for flash evaporation, respectively. The operating pressure of hydrogen separator V-101 and oxygen separator V-102 is 10-30 bar. The gas phase after flash evaporation in hydrogen separator V-101 is sent to hydrogen scrubber W-101, and the gas phase after flash evaporation in oxygen separator V-102 is sent to oxygen scrubber W-102, where demineralized water is used to wash away the alkali solution entrained in the hydrogen and oxygen. At the same time, water consumed in the production of hydrogen and oxygen is replenished, and the alkali solution concentration is maintained at a certain level.

[0142] After being washed by hydrogen scrubber W-101 and oxygen scrubber W-102, the raw hydrogen product gas and raw oxygen product gas are sent to the downstream refining section.

[0143] The liquid phase after flash evaporation in hydrogen separator V-101 enters hydrogen gradient separator V-103 for further flash evaporation. The flashed gas phase is then removed from the entrained alkali solution in release hydrogen scrubber S-101 and discharged to a safe location. The operating pressure of hydrogen gradient separator V-103 can be adjusted based on the liquid level difference between hydrogen gradient separator V-103 and oxygen gradient separator V-104. The pressure can be controlled within the range of 1–30 barA. Due to the pressure-reducing flash evaporation, the hydrogen content in the alkali solution is lowered.

[0144] The liquid phase after flash evaporation in oxygen separator V-102 enters oxygen gradient separator V-104 for further flash evaporation. The flashed gas phase is then removed from the alkaline solution in oxygen scrubber S-102 and discharged to a safe location. The operating pressure of oxygen gradient separator V-104 can be adjusted according to the operating load or current density of water electrolysis cell A-101. The pressure can be controlled between 1 and 30 barA. Due to the pressure-reducing flash evaporation, the oxygen content in the alkaline solution is lowered.

[0145] After the liquid phases from the flash evaporation of hydrogen gradient separator V-103 and oxygen gradient separator V-104 are mixed, they are sent to alkali cooler E-101 for cooling to 70-90°C, and then sent to alkali circulation pump P-101.

[0146] An alkaline solution circulation flow regulating valve FV-101 is installed on the pipeline from the circulating pump P-101 to the water electrolysis cell A-101 to control the alkaline solution circulation volume. When the load or current density of the water electrolysis unit decreases, the alkaline solution circulation volume is reduced by decreasing the opening of the alkaline solution circulation flow regulating valve FV-101.

[0147] To avoid excessive pressure difference between the cathode and anode chambers of the water electrolyzer, a liquid phase balance tube is installed between the hydrogen gradient separator V-103 and the oxygen gradient separator V-104.

[0148] The medium- and high-pressure water electrolysis device in this embodiment 1 can have its load fluctuation range extended to 15% to 100%, and the hydrogen concentration in the crude oxygen product gas is still less than 2%.

[0149] Example 2:

[0150] refer to Figure 2 The hydrogen-containing alkaline solution is pressurized to the required operating pressure of 10-30 barg in electrolytic cell A-101 by the cathode alkaline solution circulation pump P-101, and then enters the cathode chamber of electrolytic cell A-101. The oxygen-containing alkaline solution is pressurized to the required operating pressure of 10-30 barg in electrolytic cell A-101 by the anode alkaline solution circulation pump P-102, and then enters the anode chamber of electrolytic cell A-101. Under the action of electrical energy and the cathode / anode electrodes, the water in the alkaline solution decomposes, producing hydrogen and oxygen in the cathode and anode chambers, respectively. This method can solve the solution polarization problem in water electrolysis devices.

[0151] The hydrogen and oxygen produced by decomposition, along with the alkaline solution, enter hydrogen separator V-101 and oxygen separator V-102 respectively for flash evaporation. The operating pressure of hydrogen separator V-101 and oxygen separator V-102 is 10–30 bar. The gas phase after flash evaporation in hydrogen separator V-101 is sent to hydrogen scrubber W-101, and the gas phase after flash evaporation in oxygen separator V-102 is sent to oxygen scrubber W-102, where demineralized water is used to remove entrained alkaline solution from the hydrogen and oxygen. Simultaneously, water consumed in the production of hydrogen and oxygen is replenished, and the alkaline solution concentration is maintained at a certain level.

[0152] After being washed by hydrogen scrubber W-101 and oxygen scrubber W-102, the raw hydrogen product gas and raw oxygen product gas are sent to the downstream refining section.

[0153] The liquid phase after flash evaporation in hydrogen separator V-101 enters hydrogen gradient separator V-103 for further flash evaporation. The flashed gas phase is then removed from the entrained alkali solution in release hydrogen scrubber S-101 and discharged to a safe location. The operating pressure of hydrogen gradient separator V-103 can be adjusted based on the liquid level difference between hydrogen gradient separator V-103 and oxygen gradient separator V-104. The pressure can be controlled within the range of 1–30 barA. Due to the pressure-reducing flash evaporation, the hydrogen content in the alkali solution is lowered.

[0154] The liquid phase after flash evaporation in oxygen separator V-102 enters oxygen gradient separator V-104 for further flash evaporation. The flashed gas phase is then removed from the alkaline solution by oxygen release scrubber S-102 and discharged to a safe location. The operating pressure of oxygen gradient separator V-104 can be adjusted according to the operating load or current density of water electrolysis cell A-101. The pressure can be controlled between 1 and 30 barA. Due to the pressure-reducing flash evaporation, the oxygen content in the alkaline solution is lowered.

[0155] The liquid phase from the hydrogen gradient separator V-103 is sent to the cathode alkali cooler E-101 for cooling to 70~90℃, and then sent to the cathode alkali circulation pump P-101.

[0156] The liquid phase from the oxygen gradient separator V-104 is sent to the anode alkali cooler E-102 for cooling to 70~90℃, and then sent to the anode alkali circulation pump P-102.

[0157] To avoid excessive pressure difference between the cathode and anode chambers of the water electrolyzer, a liquid phase balance tube is installed between the hydrogen gradient separator V-103 and the oxygen gradient separator V-104.

[0158] Cathode alkali circulation flow regulating valves FV-101 and FV-102 are installed on the pipelines from the cathode alkali circulation pump P-101 and the anode alkali circulation pump P-102 to the water electrolysis cell A-101 to control the alkali circulation volume. When the load or current density of the water electrolysis unit decreases, the alkali circulation volume is reduced by decreasing the opening of the cathode alkali circulation flow regulating valve FV-101 and the anode alkali circulation flow regulating valve FV-102.

[0159] The medium- and high-pressure water electrolysis device in this embodiment 2 can have its load fluctuation range extended to 25% to 100%, and the hydrogen concentration in the crude oxygen product gas is still less than 2%.

[0160] Example 3:

[0161] refer to Figure 3The alkali solution is pressurized by the circulating pump P-101 to the required operating pressure of 10-30 barg in electrolytic cell A-101, and then enters the cathode and anode chambers of electrolytic cell A-101, respectively. Under the action of electrical energy and the cathode / anode electrodes, the water in the alkali solution decomposes, producing hydrogen and oxygen in the cathode and anode chambers, respectively. The hydrogen and oxygen produced by decomposition, along with the alkali solution, enter the hydrogen separator V-101 and oxygen separator V-102 for flash evaporation, respectively. The operating pressure of hydrogen separator V-101 and oxygen separator V-102 is 10-30 bar. The gas phase after flash evaporation in hydrogen separator V-101 is sent to hydrogen scrubber W-101, and the gas phase after flash evaporation in oxygen separator V-102 is sent to oxygen scrubber W-102, where demineralized water is used to wash away the alkali solution entrained in the hydrogen and oxygen. At the same time, water consumed in the production of hydrogen and oxygen is replenished, and the alkali solution concentration is maintained at a certain level.

[0162] After being washed by hydrogen scrubber W-101 and oxygen scrubber W-102, the raw hydrogen product gas and raw oxygen product gas are sent to the downstream refining section.

[0163] After flash evaporation and mixing in hydrogen separator V-101 and oxygen separator V-102, the liquid phase is divided into two flow paths. Under normal operation, all alkali solution directly enters the circulating alkali solution cooler E-101. When the current density is relatively low or when the hydrogen content in the oxygen product gas is higher than 1-2%, all alkali solution enters the gradient separator V-103 for flash evaporation. The flashed gas phase is then discharged safely after being de-entrained by the purge gas scrubber S-101. The operating pressure of the gradient separator V-103 can be controlled within the range of 1-5 barA. Due to the pressure-reducing flash evaporation, the hydrogen content in the alkali solution is lowered. Simultaneously, when the alkali solution enters the gradient separator V-103, the nitrogen valve FV-103 opens, diluting the concentration of oxygen and hydrogen in the flash vapor phase of the gradient separator V-103. The two streams of alkali solution are finally combined and enter the circulating alkali solution cooler E-101.

[0164] After being cooled by the circulating cooler E-101, the alkali solution is sent to the circulating alkali solution pump P-101 for pressurization to the required operating pressure of 10-30 barg for the water electrolyzer. After being pressurized, the alkali solution is sent to the water electrolyzer A-101 after the flow rate is regulated by the alkali solution circulation flow regulating valve FV-101.

[0165] The medium- and high-pressure water electrolysis device in this embodiment 3 can have its load fluctuation range extended to 15% to 100%, and the hydrogen concentration in the crude oxygen product gas is still less than 2%.

[0166] The present invention includes the following technical solutions.

[0167] 1. A water electrolysis device, comprising:

[0168] An electrolytic cell is used to electrolyze alkaline solutions to produce hydrogen and oxygen.

[0169] Hydrogen separator, used for hydrogen gas and entrained alkali solution generated by flash electrolysis;

[0170] An oxygen separator is used to separate the oxygen produced by flash electrolysis from the entrained alkali solution.

[0171] A hydrogen gradient separator is used to receive and flash the liquid phase after flashing in the hydrogen separator;

[0172] An oxygen gradient separator is used to receive and flash the liquid phase after flashing in an oxygen separator; and

[0173] The pipeline that returns the liquid phases after flash evaporation from the hydrogen gradient separator and the oxygen gradient separator to the electrolyzer can be either mixed or returned separately to the electrolyzer.

[0174] 2. The water electrolysis device according to technical solution 1 further includes...

[0175] Hydrogen scrubber, used to wash away alkaline solution entrained in hydrogen after flash evaporation in a hydrogen separator and to produce crude hydrogen; and / or

[0176] An oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen separator and to produce crude oxygen.

[0177] 3. The water electrolysis device according to technical solution 1 further includes...

[0178] Replenish pipelines that supply water consumed in the production of hydrogen and oxygen.

[0179] 4. The water electrolysis device according to technical solution 1 further includes...

[0180] A hydrogen purge scrubber is used to wash away the alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen gradient separator and to produce hydrogen purge gas; and / or

[0181] A purge oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen gradient separator and to produce oxygen purge gas.

[0182] 5. The water electrolysis device according to technical solution 1, wherein...

[0183] The apparatus includes a pipeline that mixes the liquid phases after flash evaporation from the hydrogen gradient separator and the oxygen gradient separator and returns them to the electrolyzer, and the pipeline includes a circulation flow regulating valve.

[0184] 6. The water electrolysis device according to technical solution 1, wherein...

[0185] The apparatus includes pipelines that return the liquid phases after flash evaporation from the hydrogen gradient separator and the oxygen gradient separator to the electrolyzer, respectively, and includes a circulation flow regulating valve in the pipelines that return the liquid phases after flash evaporation from the hydrogen gradient separator to the electrolyzer and / or the pipelines that return the liquid phases after flash evaporation from the oxygen gradient separator to the electrolyzer.

[0186] 7. The water electrolysis device according to technical solution 1 further includes...

[0187] Liquid phase balance tube between the hydrogen gradient separator and the oxygen gradient separator.

[0188] 8. The water electrolysis device according to technical solution 1, wherein the operating pressure of the electrolysis cell is 10-30 barg.

[0189] 9. The water electrolysis device according to technical solution 1, wherein the operating pressure of the hydrogen separator and the oxygen separator is 10-30 bar.

[0190] 10. The water electrolysis apparatus according to technical solution 1, wherein the operating pressure of the hydrogen gradient separator and the oxygen gradient separator is 1-30 barA.

[0191] 11. The water electrolysis device according to technical solution 1, wherein the operating pressure of the hydrogen gradient separator and the oxygen gradient separator is maintained by the gas phase flashed out of the hydrogen gradient separator and the oxygen gradient separator, or by the gas phase flashed out of the hydrogen separator and the oxygen separator, or by an inert gas.

[0192] 12. The water electrolysis apparatus according to technical solution 1 further includes a circulation pump downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the electrolysis cell.

[0193] 13. The water electrolysis apparatus according to technical solution 5 or 6 further includes a circulating alkali cooler downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali cooler.

[0194] 14. A water electrolysis device, comprising:

[0195] An electrolytic cell is used to electrolyze alkaline solutions to produce hydrogen and oxygen.

[0196] Hydrogen separator, used for hydrogen gas and entrained alkali solution generated by flash electrolysis;

[0197] An oxygen separator is used to separate the oxygen produced by flash electrolysis from the entrained alkali solution.

[0198] A gradient separator is used to receive and flash the liquid phase from the hydrogen separator and the liquid phase from the oxygen separator; and

[0199] The pipeline that returns the liquid phase after flash evaporation in the gradient separator to the electrolyzer.

[0200] 15. The water electrolysis device according to technical solution 14 further includes...

[0201] Hydrogen scrubber, used to wash away alkaline solution entrained in hydrogen after flash evaporation in a hydrogen separator and to produce crude hydrogen; and / or

[0202] An oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen separator and to produce crude oxygen.

[0203] 16. The water electrolysis device according to technical solution 14 further includes...

[0204] Replenish pipelines that supply water consumed in the production of hydrogen and oxygen.

[0205] 17. The water electrolysis device according to technical solution 14 further includes...

[0206] A purge gas scrubber is used to wash away the alkaline solution entrained in the gas after flash evaporation in the gradient separator and to generate purge gas.

[0207] 18. The water electrolysis device according to technical solution 14, wherein...

[0208] The pipeline that returns the liquid phase after flash evaporation in the gradient separator to the electrolyzer includes a circulation flow regulating valve.

[0209] 19. The water electrolysis apparatus according to technical solution 14, wherein the operating pressure of the electrolytic cell is 10-30 barg.

[0210] 20. The water electrolysis apparatus according to technical solution 14, wherein the operating pressure of the hydrogen separator and the oxygen separator is 10-30 bar.

[0211] 21. The water electrolysis apparatus according to technical solution 14, wherein the operating pressure of the gradient separator is 1-5 barA.

[0212] 22. The water electrolysis apparatus according to technical solution 14, wherein the operating pressure of the gradient separator is maintained by the gas phase flashed out by the gradient separator, or by the gas phase flashed out by the hydrogen separator and the oxygen separator, or by an inert gas.

[0213] 23. The water electrolysis apparatus according to technical solution 14 further includes a circulation pump downstream of the gradient separator and upstream of the electrolysis cell.

[0214] 24. The water electrolysis device according to technical solution 18 further includes a circulating alkali cooler downstream of the gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali cooler.

[0215] 25. A method for water electrolysis, comprising:

[0216] Hydrogen and oxygen are produced by electrolyzing an alkaline solution in an electrolytic cell.

[0217] Hydrogen and entrained alkaline solution produced by flash electrolysis in a hydrogen separator;

[0218] Oxygen and entrained alkali solution produced by flash electrolysis in an oxygen separator;

[0219] The liquid phase after flashing in the hydrogen separator is received and flashed through the hydrogen gradient separator;

[0220] The liquid phase after flashing in the oxygen separator is received and flashed through the oxygen gradient separator; and

[0221] The liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator are mixed and returned to the electrolytic cell, or the liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator are returned to the electrolytic cell separately.

[0222] 26. The water electrolysis method according to technical solution 25 further includes...

[0223] The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen separator is washed away by a hydrogen scrubber, producing crude hydrogen; and / or

[0224] The oxygen scrubber removes the alkaline solution entrained in the oxygen after flash evaporation in the oxygen separator and produces crude oxygen.

[0225] 27. The water electrolysis method according to technical solution 25 further includes...

[0226] Replenish the water consumed in the production of hydrogen and oxygen.

[0227] 28. The water electrolysis method according to technical solution 25 further includes...

[0228] The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen gradient separator is washed away by a hydrogen purge scrubber, and hydrogen purge gas is generated; and / or

[0229] The oxygen is washed away by a release oxygen scrubber to remove the alkaline solution entrained in the oxygen after flash evaporation in the oxygen gradient separator and to produce oxygen release gas.

[0230] 29. The water electrolysis method according to technical solution 25 further includes...

[0231] The circulation volume of alkali solution is controlled by a circulation flow regulating valve in the pipeline that returns the liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator to the electrolyzer. Specifically, the circulation volume of alkali solution is reduced when the load or current density of the water electrolysis unit decreases.

[0232] 30. The water electrolysis method according to technical solution 25 further includes...

[0233] The alkali circulation volume is controlled by a circulation flow regulating valve included in the pipeline that returns the liquid phase after flash evaporation from the hydrogen gradient separator to the electrolyzer and / or in the pipeline that returns the liquid phase after flash evaporation from the oxygen gradient separator to the electrolyzer, wherein the alkali circulation volume is reduced when the load or current density of the water electrolysis unit decreases.

[0234] 31. The water electrolysis method according to technical solution 25 further includes...

[0235] The pressure difference between the cathode and anode chambers of the electrolyzer is reduced by using a liquid phase balance tube between the hydrogen gradient separator and the oxygen gradient separator.

[0236] 32. The water electrolysis method according to technical solution 25, wherein the operating pressure of the electrolytic cell is 10-30 barg.

[0237] 33. The water electrolysis method according to technical solution 25, wherein the operating pressure of the hydrogen separator and the oxygen separator is 10-30 bar.

[0238] 34. The water electrolysis method according to technical solution 25, wherein the operating pressure of the hydrogen gradient separator and the oxygen gradient separator is 1-30 barA.

[0239] 35. The water electrolysis method according to technical solution 25, wherein the operating pressure of the hydrogen gradient separator is adjusted according to the liquid level difference between the hydrogen gradient separator and the oxygen gradient separator.

[0240] 36. The water electrolysis method according to technical solution 25, wherein the operating pressure of the hydrogen gradient separator and / or the oxygen gradient separator is adjusted according to the operating load or current density of the electrolyzer.

[0241] 37. The water electrolysis method according to technical solution 25, wherein the operating pressure of the hydrogen gradient separator and the oxygen gradient separator is maintained by the gas phase flashed out of the hydrogen gradient separator and the oxygen gradient separator, or by the gas phase flashed out of the hydrogen separator and the oxygen separator, or by an inert gas.

[0242] 38. The water electrolysis method according to technical solution 25 further includes circulating the alkaline solution through a circulation pump downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the electrolyzer.

[0243] 39. The water electrolysis method according to technical solution 29 or 30 further includes cooling the alkali solution by a circulating alkali solution cooler downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali solution cooler.

[0244] 40. A method for water electrolysis, comprising:

[0245] Hydrogen and oxygen are produced by electrolyzing an alkaline solution in an electrolytic cell.

[0246] Hydrogen and entrained alkaline solution produced by flash electrolysis in a hydrogen separator;

[0247] Oxygen and entrained alkali solution produced by flash electrolysis in an oxygen separator;

[0248] The gradient separator receives and flashes the liquid phase from the hydrogen separator and the liquid phase from the oxygen separator; and

[0249] The liquid phase after flash evaporation in the gradient separator is returned to the electrolytic cell.

[0250] 41. The water electrolysis method according to technical solution 40 further includes...

[0251] The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen separator is washed away by a hydrogen scrubber, producing crude hydrogen; and / or

[0252] The oxygen scrubber removes the alkaline solution entrained in the oxygen after flash evaporation in the oxygen separator and produces crude oxygen.

[0253] 42. The water electrolysis method according to technical solution 40 further includes...

[0254] Replenish the water consumed in the production of hydrogen and oxygen.

[0255] 43. The water electrolysis method according to technical solution 40 further includes...

[0256] The alkali entrained in the gas after flash evaporation in the gradient separator is washed away by the vent gas scrubber, and vent gas is generated.

[0257] 44. The water electrolysis method according to technical solution 40 further includes...

[0258] The amount of alkali solution circulating is controlled by a circulation flow regulating valve included in the pipeline that returns the liquid phase after flash evaporation in the gradient separator to the electrolyzer.

[0259] 45. The water electrolysis method according to technical solution 40, wherein the operating pressure of the electrolytic cell is 10-30 barg.

[0260] 46. ​​The water electrolysis method according to technical solution 40, wherein the operating pressure of the hydrogen separator and the oxygen separator is 10-30 bar.

[0261] 47. The water electrolysis method according to technical solution 40, wherein the operating pressure of the gradient separator is 1-5 barA.

[0262] 48. The water electrolysis method according to technical solution 40, wherein the operating pressure of the gradient separator is adjusted according to the operating load or current density of the electrolyzer.

[0263] 49. The water electrolysis method according to technical solution 40, wherein the operating pressure of the gradient separator is maintained by the gas phase flashed out by the gradient separator, or by the gas phase flashed out by the hydrogen separator and the oxygen separator, or by an inert gas.

[0264] 50. The water electrolysis method according to technical solution 40 further includes circulating the alkaline solution via a circulation pump located downstream of the gradient separator and upstream of the electrolytic cell.

[0265] 51. The water electrolysis method according to technical solution 44 further includes cooling the alkali solution by a circulating alkali solution cooler located downstream of the gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali solution cooler.

[0266] 52. The water electrolysis method according to technical solution 40, wherein when the liquid phase enters the gradient separator, the hydrogen and oxygen in the gas phase generated by flash evaporation in the gradient separator are diluted with an inert gas.

[0267] Although the invention has been described with reference to the preferred embodiments depicted in the accompanying drawings, it will be understood that various modifications are possible within the spirit or scope of the invention.

Claims

1. A water electrolysis device, comprising: An electrolytic cell is used to electrolyze alkaline solutions to produce hydrogen and oxygen. Hydrogen separator, used for hydrogen gas and entrained alkali solution generated by flash electrolysis; An oxygen separator is used to separate the oxygen produced by flash electrolysis from the entrained alkali solution. A hydrogen gradient separator is used to receive and flash the liquid phase after flashing in the hydrogen separator; An oxygen gradient separator is used to receive and flash the liquid phase after flashing in an oxygen separator; as well as A pipeline for returning the liquid phases after flash evaporation from the hydrogen gradient separator and the oxygen gradient separator to the electrolyzer, wherein the pipeline includes a circulation flow regulating valve; or pipelines for returning the liquid phases after flash evaporation from the hydrogen gradient separator and the oxygen gradient separator to the electrolyzer separately, wherein the pipelines for returning the liquid phases after flash evaporation from the hydrogen gradient separator to the electrolyzer and / or the pipelines for returning the liquid phases after flash evaporation from the oxygen gradient separator to the electrolyzer include circulation flow regulating valves; and The operating pressure of the hydrogen gradient separator and the oxygen gradient separator is maintained by the gas phase flashed out of the hydrogen gradient separator and the oxygen gradient separator, or by the gas phase flashed out of the hydrogen separator and the oxygen separator, or by an inert gas.

2. The water electrolysis device according to claim 1, further comprising: Hydrogen scrubber, used to wash away alkaline solution entrained in hydrogen after flash evaporation in a hydrogen separator and to produce crude hydrogen; and / or An oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen separator and to produce crude oxygen.

3. The water electrolysis device according to claim 1, further comprising: Replenish pipelines that supply water consumed in the production of hydrogen and oxygen.

4. The water electrolysis device according to claim 1, further comprising: A hydrogen purge scrubber is used to wash away the alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen gradient separator and to produce hydrogen purge gas; and / or A purge oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen gradient separator and to produce oxygen purge gas.

5. The water electrolysis apparatus according to claim 1, further comprising: Liquid phase balance tube between the hydrogen gradient separator and the oxygen gradient separator.

6. The water electrolysis apparatus according to claim 1, wherein the operating pressure of the electrolytic cell is 10-30 barg.

7. The water electrolysis apparatus according to claim 1, wherein the operating pressure of the hydrogen separator and the oxygen separator is 10-30 bar.

8. The water electrolysis apparatus according to claim 1, wherein the operating pressure of the hydrogen gradient separator and the oxygen gradient separator is 1-30 barA.

9. The water electrolysis apparatus according to claim 1 further includes a circulation pump downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the electrolyzer.

10. The water electrolysis apparatus according to claim 1 further includes a circulating alkali cooler downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali cooler.

11. A water electrolysis device, comprising: An electrolytic cell is used to electrolyze alkaline solutions to produce hydrogen and oxygen. Hydrogen separator, used for hydrogen gas and entrained alkali solution generated by flash electrolysis; An oxygen separator is used to separate the oxygen produced by flash electrolysis from the entrained alkali solution. Gradient separator, used to receive and flash the liquid phase after flashing in the hydrogen separator and the liquid phase after flashing in the oxygen separator; as well as A pipeline for returning the liquid phase after flash evaporation in the gradient separator to the electrolyzer includes a circulation flow regulating valve. The operating pressure of the gradient separator is maintained by the gas phase flashed out by the gradient separator, or by the gas phase flashed out by the hydrogen separator and oxygen separator, or by an inert gas.

12. The water electrolysis apparatus according to claim 11, further comprising: Hydrogen scrubber, used to wash away alkaline solution entrained in hydrogen after flash evaporation in a hydrogen separator and to produce crude hydrogen; and / or An oxygen scrubber is used to wash away the alkaline solution entrained in the oxygen after flash evaporation in an oxygen separator and to produce crude oxygen.

13. The water electrolysis apparatus according to claim 11, further comprising: Replenish pipelines that supply water consumed in the production of hydrogen and oxygen.

14. The water electrolysis apparatus according to claim 11, further comprising: A purge gas scrubber is used to wash away the alkaline solution entrained in the gas after flash evaporation in the gradient separator and to generate purge gas.

15. The water electrolysis apparatus according to claim 11, wherein the operating pressure of the electrolyzer is 10-30 barg.

16. The water electrolysis apparatus according to claim 11, wherein the operating pressure of the hydrogen separator and the oxygen separator is 10-30 bar.

17. The water electrolysis apparatus according to claim 11, wherein the operating pressure of the gradient separator is 1-5 barA.

18. The water electrolysis apparatus of claim 11, further comprising a circulation pump downstream of the gradient separator and upstream of the electrolyzer.

19. The water electrolysis apparatus according to claim 11 further includes a circulating alkali cooler downstream of the gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali cooler.

20. A method for water electrolysis, comprising: Hydrogen and oxygen are produced by electrolyzing an alkaline solution in an electrolytic cell. Hydrogen and entrained alkaline solution produced by flash electrolysis in a hydrogen separator; Oxygen and entrained alkali solution produced by flash electrolysis in an oxygen separator; The liquid phase after flashing in the hydrogen separator is received and flashed through the hydrogen gradient separator; The liquid phase after flashing in the oxygen separator is received and flashed through the oxygen gradient separator; and The liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator are mixed and returned to the electrolyzer. The circulation rate of the alkali solution is controlled by a flow regulating valve in the pipeline used to return the mixed liquid phases to the electrolyzer. When the load or current density of the water electrolysis unit decreases, the alkali circulation rate is reduced; or the liquid phases after flash evaporation in the hydrogen gradient separator and oxygen gradient separator are returned to the electrolyzer, respectively. The alkali circulation rate is controlled by a circulation flow regulating valve included in the pipeline returning the liquid phase after flash evaporation from the hydrogen gradient separator to the electrolyzer and / or in the pipeline returning the liquid phase after flash evaporation from the oxygen gradient separator to the electrolyzer. Specifically, when the load or current density of the water electrolysis unit decreases, the alkali circulation rate is reduced. The operating pressure of the hydrogen gradient separator and the oxygen gradient separator is maintained by the gas phase flashed out of the hydrogen gradient separator and the oxygen gradient separator, or by the gas phase flashed out of the hydrogen separator and the oxygen separator, or by an inert gas.

21. The water electrolysis method according to claim 20, further comprising: The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen separator is washed away by a hydrogen scrubber, producing crude hydrogen; and / or The oxygen scrubber removes the alkaline solution entrained in the oxygen after flash evaporation in the oxygen separator and produces crude oxygen.

22. The water electrolysis method according to claim 20, further comprising: Replenish the water consumed in the production of hydrogen and oxygen.

23. The water electrolysis method according to claim 20, further comprising: The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen gradient separator is washed away by a hydrogen purge scrubber, and hydrogen purge gas is generated; and / or The oxygen is washed away by a release oxygen scrubber to remove the alkaline solution entrained in the oxygen after flash evaporation in the oxygen gradient separator and to produce oxygen release gas.

24. The water electrolysis method according to claim 20, further comprising: The pressure difference between the cathode and anode chambers of the electrolyzer is reduced by using a liquid phase balance tube between the hydrogen gradient separator and the oxygen gradient separator.

25. The water electrolysis method according to claim 20, wherein the operating pressure of the electrolytic cell is 10-30 barg.

26. The water electrolysis method according to claim 20, wherein the operating pressure of the hydrogen separator and the oxygen separator is 10-30 bar.

27. The water electrolysis method according to claim 20, wherein the operating pressure of the hydrogen gradient separator and the oxygen gradient separator is 1-30 barA.

28. The water electrolysis method according to claim 20, wherein the operating pressure of the hydrogen gradient separator is adjusted according to the liquid level difference between the hydrogen gradient separator and the oxygen gradient separator.

29. The water electrolysis method according to claim 20, wherein the operating pressure of the hydrogen gradient separator and / or the oxygen gradient separator is adjusted according to the operating load or current density of the electrolyzer.

30. The water electrolysis method according to claim 20 further includes circulating the alkaline solution via a circulation pump downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the electrolyzer.

31. The water electrolysis method according to claim 20 further includes cooling the alkali solution by a circulating alkali solution cooler downstream of the hydrogen gradient separator and / or oxygen gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali solution cooler.

32. A method for water electrolysis, comprising: Hydrogen and oxygen are produced by electrolyzing an alkaline solution in an electrolytic cell. Hydrogen and entrained alkaline solution produced by flash electrolysis in a hydrogen separator; Oxygen and entrained alkali solution produced by flash electrolysis in an oxygen separator; The gradient separator receives and flashes the liquid phase from the hydrogen separator and the liquid phase from the oxygen separator; and The liquid phase after flash evaporation in the gradient separator is returned to the electrolyzer, wherein the circulation rate of the alkali solution is controlled by a circulation flow regulating valve included in the pipeline for returning the liquid phase after flash evaporation in the gradient separator to the electrolyzer, and wherein the operating pressure of the gradient separator is maintained by the gas phase flashed out by the gradient separator, or by the gas phase flashed out by the hydrogen separator and oxygen separator, or by an inert gas.

33. The water electrolysis method according to claim 32, further comprising: The alkaline solution entrained in the hydrogen after flash evaporation in the hydrogen separator is washed away by a hydrogen scrubber, producing crude hydrogen; and / or The oxygen scrubber removes the alkaline solution entrained in the oxygen after flash evaporation in the oxygen separator and produces crude oxygen.

34. The water electrolysis method according to claim 32, further comprising: Replenish the water consumed in the production of hydrogen and oxygen.

35. The water electrolysis method according to claim 32, further comprising: The alkali entrained in the gas after flash evaporation in the gradient separator is washed away by the vent gas scrubber, and vent gas is generated.

36. The water electrolysis method according to claim 32, wherein the operating pressure of the electrolytic cell is 10-30 barg.

37. The water electrolysis method according to claim 32, wherein the operating pressure of the hydrogen separator and the oxygen separator is 10-30 bar.

38. The water electrolysis method according to claim 32, wherein the operating pressure of the gradient separator is 1-5 barA.

39. The water electrolysis method according to claim 32, wherein the operating pressure of the gradient separator is adjusted according to the operating load or current density of the electrolyzer.

40. The water electrolysis method according to claim 32 further includes circulating the alkali solution via a circulation pump located downstream of the gradient separator and upstream of the electrolyzer.

41. The water electrolysis method according to claim 32 further includes cooling the alkali solution by a circulating alkali solution cooler downstream of the gradient separator and upstream of the circulating flow regulating valve, wherein the opening of the circulating flow regulating valve is adjusted by the temperature difference at the hot end of the circulating alkali solution cooler.

42. The water electrolysis method according to claim 32, wherein after the liquid phase enters the gradient separator, the hydrogen and oxygen in the gas phase generated by flash evaporation in the gradient separator are diluted with an inert gas.

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