High differential pressure water electrolysis system and method for starting the same
A high differential pressure water electrolysis system includes a high differential pressure water electrolysis device, a water supply tank, a high pressure gas-liquid separator, a hydrogen outlet line, a drain line, a low pressure gas-liquid separator, a water return line, and a pressure maintaining mechanism. The drain line is to drain a liquid water separated by the high pressure gas-liquid separator. The low pressure gas-liquid separator is disposed in the drain line and has a discharge line via which a gas separated by the low pressure gas-liquid separator is to be discharged. The water return line connects the low pressure gas-liquid separator and the water supply tank. The pressure maintaining mechanism is disposed in the discharge line and configured to maintain a pressure in the low pressure gas-liquid separator to be higher than a pressure in the water supply tank.
1. A high differential pressure water electrolysis system comprising:
a high differential pressure water electrolysis device configured to electrolyze water to generate oxygen and high pressure hydrogen which has a pressure higher than a pressure of the oxygen;
a water supply tank to store the water to be supplied to the high differential pressure water electrolysis device;
a high pressure gas-liquid separator to separate liquid from the high pressure hydrogen output from the high differential pressure water electrolysis device;
a hydrogen outlet line connecting the high differential pressure water electrolysis device and the high pressure gas-liquid separator;
a drain line to drain a liquid water separated by the high pressure gas-liquid separator;
a low pressure gas-liquid separator disposed in the drain line and having a discharge line via which a gas separated by the low pressure gas-liquid separator is to be discharged;
a water return line connecting the low pressure gas-liquid separator and the water supply tank; and
a pressure maintaining mechanism disposed in the discharge line and configured to maintain a pressure in the low pressure gas-liquid separator to be higher than a pressure in the water supply tank.
2. The high differential pressure water electrolysis system according to claim 1 , further comprising a drain decompression mechanism disposed on the drain line, the low pressure gas-liquid separator being located downstream of the drain decompression mechanism.
3. The high differential pressure water electrolysis system according to claim 1 ,
wherein the water supply tank has an air blower configured to dilute a gas component from which liquid is separated in the water supply tank, and
the pressure maintaining mechanism is set at a pressure higher than a back pressure that acts on the water supply tank when the air blower drives with maximum performance.
4. The high differential pressure water electrolysis system according to claim 1 , further comprising a pressure application line configured to connect a midpoint of the hydrogen outlet line and the low pressure gas-liquid separator,
wherein the pressure application line is provided with a decompression mechanism and an opening and closing valve, and an outlet pressure of the decompression mechanism is set to be higher than a pressure in the water supply tank.
5. A method for starting a high differential pressure water electrolysis system that includes:
a high differential pressure water electrolysis device configured to electrolyze water to generate oxygen and high pressure hydrogen which has a pressure higher than a pressure of the oxygen;
a water supply tank to store the water to be supplied to the high differential pressure water electrolysis device;
a high pressure gas-liquid separator to separate liquid from the high pressure hydrogen output from the high differential pressure water electrolysis device;
a hydrogen outlet line connecting the high differential pressure water electrolysis device and the high pressure gas-liquid separator;
a drain line to drain a liquid water separated by the high pressure gas-liquid separator;
a low pressure gas-liquid separator disposed in the drain line;
a water return line connecting the low pressure gas-liquid separator and the water supply tank; and
a pressure application line connecting a midpoint of the hydrogen outlet line and the low pressure gas-liquid separator,
the method comprising:
determining whether or not a pressure in the low pressure gas-liquid separator is lower than a pressure in the water supply tank;
introducing the high pressure hydrogen output from the high differential pressure water electrolysis device into the low pressure gas-liquid separator through the pressure application line when it is determined that the pressure in the low pressure gas-liquid separator is lower than the pressure in the water supply tank; and
opening the water return line to return water in the low pressure gas-liquid separator to the water supply tank when it is determined that the pressure in the low pressure gas-liquid separator is higher than the pressure in the water supply tank.
6. The method according to claim 5 , further comprising:
providing a drain decompression mechanism in the drain line upstream of the low pressure gas-liquid separator.
7. The method according to claim 5 , further comprising:
providing an air blower in the water supply tank, the air blower being configured to dilute a gas component from which liquid is separated in the water supply tank; and
setting a pressure in the low pressure gas-liquid separator at a pressure higher than a back pressure that acts on the water supply tank when the air blower drives with maximum performance.