Water electrolysis apparatus

Abstract

To provide a water electrolysis apparatus that satisfactorily suppresses performance degradation and deterioration of a blower that re-circulates hydrogen generated in a water electrolysis module to the water electrolysis module.SOLUTION: The water electrolysis apparatus of the present disclosure comprises a water electrolysis module that generates hydrogen by steam electrolysis, a blower for supplying hydrogen to the water electrolysis module, a recycle passage that supplies generated hydrogen generated in the water electrolysis module from the water electrolysis module to a suction port of the blower, a condenser that condenses water vapor contained in the generated hydrogen, and a temperature raising section that raises the temperature of the generated hydrogen between the condenser and the blower.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a water electrolysis device including a water electrolysis module that produces hydrogen by steam electrolysis. [Background technology]

[0002] Conventionally, there is known a water electrolysis apparatus in which hydrogen produced at the fuel electrode of a water electrolysis cell is mixed with steam supplied to the fuel electrode and the mixture is recycled to the water electrolysis cell (see, for example, Patent Document 1). In this water electrolysis apparatus, fuel electrode off-gas cooled by a cooler is supplied to a phase separator, and the gas that has passed through the phase separator is pressurized by a blower and then mixed with steam. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2018-517233 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-described conventional water electrolysis apparatus, gas containing saturated water vapor in addition to hydrogen may be supplied to the blower from the phase separator, and the water vapor may condense inside the blower, potentially resulting in performance degradation or deterioration of the blower.

[0005] Therefore, a main object of the present disclosure is to provide a water electrolysis device that can effectively suppress performance degradation and deterioration of a blower that recirculates hydrogen generated in a water electrolysis module to the water electrolysis module. [Means for solving the problem]

[0006] The water electrolysis device disclosed herein includes a water electrolysis module that generates hydrogen by steam electrolysis, a blower that supplies hydrogen to the water electrolysis module, a recycle passage that supplies hydrogen generated in the water electrolysis module from the water electrolysis module to an inlet of the blower, a condenser that condenses water vapor contained in the generated hydrogen, and a heating unit that heats the generated hydrogen between the condenser and the blower.

[0007] In the water electrolysis apparatus disclosed herein, hydrogen produced in the water electrolysis module is supplied from the water electrolysis module to an inlet of a blower through a recycle passage. Water vapor contained in the produced hydrogen is condensed in a condenser. The produced hydrogen that has passed through the condenser is heated by a heating unit between the condenser and the blower. The heated produced hydrogen is then supplied to the water electrolysis module by the heating unit. This prevents produced hydrogen at or below its dew point temperature from being supplied to the blower from the recycle passage, thereby preventing water vapor from condensing in the recycle passage or the blower. This effectively prevents performance degradation and deterioration of the blower that recirculates hydrogen produced in the water electrolysis module to the water electrolysis module. The blower may supply hydrogen for anti-oxidation to the anode of the water electrolysis cell. The blower may supply hydrogen for combustion to a combustor included in the water electrolysis module. The water electrolysis module may include a reversible water electrolysis cell that generates electricity through an electrochemical reaction between hydrogen supplied to the anode and oxygen supplied to the oxidizer electrode. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic configuration diagram showing a water electrolysis device according to the present disclosure. [Figure 2] FIG. 1 is a system diagram showing a water electrolysis apparatus according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, embodiments of the present disclosure will be described with reference to the drawings.

[0010] Fig. 1 is a schematic diagram illustrating a water electrolysis apparatus 1 according to the present disclosure, and Fig. 2 is a system diagram illustrating the water electrolysis apparatus 1. The water electrolysis apparatus 1 illustrated in these drawings includes multiple (two in this embodiment) water electrolysis modules 2, a power supply 3, a steam generator 4, multiple (two in this embodiment) air blowers 5, a condenser 6, multiple (two in this embodiment) hydrogen blowers 7 for combustion, multiple (two in this embodiment) hydrogen blowers 8 for oxidation prevention, a water tank 9, and a housing 10 that accommodates these components. For ease of explanation, Fig. 2 shows only one of the two water electrolysis modules 2.

[0011] As shown in FIG. 1 , the water electrolysis modules 2 are arranged vertically or horizontally in the upper part of the housing 10. Each water electrolysis module 2 includes a water electrolysis cell stack 20 that produces hydrogen through steam electrolysis. The water electrolysis cell stack 20 includes a plurality of solid oxide electrolysis cells (SOECs, hereinafter referred to as "single cells") stacked in a predetermined direction. Each single cell includes an electrolyte 20a, a fuel electrode 20b disposed on one side of the electrolyte 20a, and an oxidant electrode 20c disposed on the other side of the electrolyte 20a.

[0012] The electrolyte 20a is a solid electrolyte such as stabilized zirconia (e.g., YSZ). The fuel electrode 20b is formed of a composite material of a catalytic metal such as Ni and stabilized zirconia. The oxidizer electrode 20c is formed of a ceramic such as LSCF. Each unit cell electrolyzes water vapor in a high-temperature environment of, for example, 650-800°C in response to the application of power (DC power) from the power supply 3, producing hydrogen at the fuel electrode 20b and oxygen at the oxidizer electrode 20c. Furthermore, in this embodiment, the unit cells of the water electrolysis cell stack 20 are reversible water electrolysis cells that produce hydrogen and oxygen through steam electrolysis and generate electricity through an electrochemical reaction between the hydrogen and oxygen to transmit the electricity to a power grid or the like.

[0013] Each water electrolysis module 2 includes various pipes, multiple heat exchangers, etc. in addition to the water electrolysis cell stack 20, and these components of the water electrolysis module 2 are housed in a module case 21 formed by wrapping thermal insulation around housing parts. As shown in Fig. 2 , a fuel supply pipe L1 forming a fuel supply passage is connected to the anode inlet of the water electrolysis cell stack 20 of each water electrolysis module 2. The fuel supply pipe L1 of each water electrolysis module 2 is connected to a steam generator 4 installed outside the housing 10 of the water electrolysis apparatus 1 via heat exchangers 22 and 23 in the module case 21.

[0014] A hydrogen flow pipe L2 is connected to the anode outlet of the water electrolysis cell stack 20 of each water electrolysis module 2, and anode off-gas containing hydrogen (produced hydrogen) produced at the anode 20b of each unit cell and water vapor flows into the hydrogen flow pipe L2. The hydrogen flow pipe L2 from each water electrolysis cell stack 20 is connected to a heat exchanger 24 in the module case 21 and the heat exchanger 23 via the condenser 6 outside the module case 21. That is, the anode off-gas is supplied as a heating medium (heat source) to the heat exchangers 23, 24 via the hydrogen flow pipe L2, and the anode off-gas that has passed through the heat exchangers 23, 24 of each water electrolysis module 2 is supplied to the condenser 6 via the hydrogen flow pipe L2.

[0015] Furthermore, an air supply pipe L3 forming an air supply passage is connected to an oxidant electrode inlet of the water electrolysis cell stack 20 of each water electrolysis module 2. The air supply pipe L3 from each water electrolysis cell stack 20 is connected to an air blower 5 outside the module case 21 via the heat exchangers 24 and 25 inside the module case 21. Furthermore, an oxidant electrode outlet of the water electrolysis cell stack 20 of each water electrolysis module 2 is connected to a combustor 26 via an oxidant electrode off-gas pipe L4 forming an oxidant electrode off-gas passage. Oxygen-containing oxidant electrode off-gas from the oxidant electrode 20c of each unit cell flows into the combustor 26 inside the module case 21 via the oxidant electrode off-gas pipe L4.

[0016] The combustor 26 of each water electrolysis module 2 includes an ignition device (not shown), and combusts a mixed gas of oxidant electrode off-gas from the oxidant electrode off-gas pipe L4 and hydrogen supplied from the corresponding hydrogen blower 7 outside the module case 21 via a hydrogen supply pipe (hydrogen supply passage) L5. The combustion exhaust gas generated by the combustion of the mixed gas in the combustor 26 is supplied as a heating medium to the heat exchangers 22 and 25 via an exhaust gas pipe (exhaust gas passage) L6. The exhaust gas that has passed through the heat exchangers 22 and 25 is discharged to the outside of the housing 10 of the water electrolysis apparatus 1 via the exhaust gas pipe L6. In addition, a flow meter F7 that measures the flow rate of hydrogen delivered from the hydrogen blower 7 is installed in the hydrogen supply pipe L5.

[0017] The power supply device 3 may be powered by at least one of a grid power supply and a renewable energy power generation facility, or may be a storage battery, or may be a combination of these. The power supply device 3, together with auxiliary equipment A including a control device, etc., is disposed in the lower part of the housing 10 so as to be located below each water electrolysis module 2 (see FIG. 1 ).

[0018] The steam generator 4 vaporizes raw water using a heat pump or the like (not shown) and supplies the resulting steam to the fuel supply pipe L1 of each water electrolysis module 2. The steam from the steam generator 4 is heated by heat exchange with the combustion exhaust gas in the heat exchanger 23 in the module case 21 of each water electrolysis module 2, and then heated to a required temperature by heat exchange with the anode off-gas in the heat exchanger 22. The heated steam is supplied to the anode 20b of each unit cell via the fuel supply pipe L1 and the anode inlet of the water electrolysis cell stack 20.

[0019] The air blower 5 is installed inside the housing 10 of the water electrolysis apparatus 1, above the power supply device 3 and the auxiliary machinery A, and outside the module case 21 of each water electrolysis module 2 (see FIG. 1 ). The air blower 5 draws in and discharges air from inside the housing 10 of the water electrolysis apparatus 1 via an air filter (not shown). The air from the air blower 5 is heated by heat exchange with the combustion exhaust gas in the heat exchanger 25 in the module case 21 of each water electrolysis module 2, and then heated to a required temperature by heat exchange with the anode off-gas in the heat exchanger 24. The air is then supplied to the oxidant electrode 20c of each unit cell via the air supply pipe L3 and the oxidant electrode inlet of the water electrolysis cell stack 20. This allows oxygen generated at the oxidant electrode 20c of each unit cell to flow into the oxidant electrode off-gas pipe L4 together with the air from the air blower 5, i.e., the sweep gas.

[0020] The condenser 6 is installed inside the housing 10 of the water electrolysis apparatus 1, above the power supply 3 and the auxiliary machinery A, and outside the module case 21 of each water electrolysis module 2 (see FIG. 1 ). The condenser 6 cools the anode off-gas from the hydrogen flow pipe L2 with cold water supplied from outside the housing 10 of the water electrolysis apparatus 1, and condenses the water vapor contained in the anode off-gas (produced hydrogen). The condensed water generated by the condenser 6 is collected (stored) in a water tank 9 inside the housing 10, and the condensed water in the water tank 9 is used as raw water for generating water vapor in the steam generator 4. Furthermore, the anode off-gas, i.e., hydrogen, after gas-liquid separation in the condenser 6 flows into a booster 11, such as a diaphragm type, piston type, or centrifugal type, via a hydrogen flow pipe (hydrogen passage) L7 and is pressure-fed by the booster 11 into a hydrogen tank 12. As a result, the hydrogen generated by each water electrolysis module 2 is stored in the hydrogen tank 12. As shown in FIGS. 1 and 2, the booster 11 and the hydrogen tank 12 are installed outside the housing 10 of the water electrolysis apparatus 1.

[0021] Furthermore, a recycle pipe L8 forming a recycle passage branches off from the hydrogen flow pipe L7, and the recycle pipe L8 is connected to the inlets of each hydrogen blower 7, 8. As a result, each hydrogen blower 7 draws in a portion of the anode off-gas, i.e., hydrogen, obtained through gas-liquid separation in the condenser 6, via the recycle pipe L8, and supplies the hydrogen to the combustor 26 of the corresponding water electrolysis module 2 via the hydrogen supply pipe L5. Furthermore, each hydrogen blower 8 draws in a portion of the anode off-gas, i.e., hydrogen (produced hydrogen), obtained through gas-liquid separation in the condenser 6, via the recycle pipe L8, and discharges the hydrogen into the corresponding fuel supply pipe L1 outside the module case 21 of the corresponding water electrolysis module 2. That is, each hydrogen blower 8 mixes hydrogen from the condenser 6 as an antioxidant with the steam supplied from the steam generator 4 to the fuel supply pipe L1. This makes it possible to maintain a reducing atmosphere around the anode 20b of each unit cell in each water electrolysis cell stack 20, thereby effectively suppressing oxidation of the catalytic metal.

[0022] Each of the hydrogen blowers 7, 8 is also installed inside the housing 10 of the water electrolysis apparatus 1, above the power supply device 3 and the auxiliary machinery A, and outside the module case 21 of each of the water electrolysis modules 2 (see FIG. 1 ). Furthermore, a flow meter F8 that measures the flow rate of hydrogen taken in by the hydrogen blower 8 is installed upstream of the inlet of each of the hydrogen blowers 8. The recycle pipe L8 is also connected via piping to the hydrogen tank 12 outside the housing 10. This allows hydrogen stored in the hydrogen tank 12 to be supplied by each of the hydrogen blowers 8 to the anode inlet of the water electrolysis cell stack 20 of each of the water electrolysis modules 2 via the fuel supply pipe L1 when each of the water electrolysis cell stacks 20 is started up or when each of the water electrolysis cell stacks 20 is operated as a fuel cell.

[0023] The housing 10 of the water electrolysis apparatus 1 is made of metal or the like, and has an air intake 13 formed in the bottom of the housing 10 for ventilating the interior. The air intake 13 communicates with the interior of the housing 10 via an air filter 14 installed on the inner bottom surface of the housing 10. An exhaust duct 16 defining an exhaust port 15 is fixed to the upper part of the side wall of the housing 10. An electric ventilation fan 17 is installed at the air inlet of the exhaust duct 16.

[0024] As a result, when the ventilation fan 17 is operated while the water electrolysis apparatus 1 is in operation, external air flows into the housing 10 through the air intake 13 and the air filter 14. The air that has flowed into the housing 10 absorbs heat emitted from the water electrolysis modules 2, the power supply device 3, the auxiliary machinery A, the air blowers 5, the condenser 6, the hydrogen blowers 7 and 8, the fuel supply pipe L1, the hydrogen distribution pipe L2, the exhaust gas pipe L6, etc., inside the housing 10, and thereby increases in temperature. Furthermore, the air that has been heated inside the housing 10 is drawn into the exhaust duct 16 by the ventilation fan 17 and is discharged to the outside through the exhaust port 15.

[0025] During operation of the water electrolysis apparatus 1, the temperature around the ventilation fan 17 in the housing 10 becomes sufficiently higher (e.g., approximately 50-55°C) than the temperature (dew point temperature, e.g., approximately 30-40°C) of the anode off-gas, i.e., hydrogen, at the anode off-gas outlet of the condenser 6. In light of this, in the water electrolysis apparatus 1, a portion of the hydrogen flow pipe L7 forming the recycle passage and a portion of the recycle pipe L8 located between the hydrogen flow pipe L7 and each of the hydrogen blowers 7 and each of the flow meters F8 are disposed in the housing 10 so as to face the air inlet of the ventilation fan 17 (exhaust duct 16). That is, a portion of the hydrogen flow pipe L7 and a portion of the recycle pipe L8 form a heating section 18 that heats the anode off-gas, i.e., hydrogen, between the condenser 6 and each of the hydrogen blowers 7 and each of the flow meters F8. As can be seen from FIG. 1 , the heating section 18 is closer to the exhaust port 15 than the air inlet 13 of the housing 10.

[0026] As described above, the water electrolysis device 1 includes the water electrolysis module 2 including the water electrolysis cell stack 20, hydrogen blowers 7 and 8, hydrogen flow pipes L2 and L7, a recycle pipe L8, a condenser 6, and a heating unit 18. The water electrolysis cell stack 20 includes a plurality of unit cells that generate hydrogen at the anode 20b and oxygen at the oxidizer electrode 20c through steam electrolysis. The hydrogen blower 7 supplies hydrogen for combustion to the combustor 26 of the water electrolysis module 2, and the hydrogen blower 8 supplies hydrogen for oxidation prevention to the anode 20b of each unit cell in the water electrolysis cell stack 20. The hydrogen flow pipes L2 and L7 and the recycle pipe L8 form a recycle passage that supplies hydrogen-containing anode off-gas (produced hydrogen) from the anode 20b of each unit cell in the water electrolysis cell stack 20 to the inlet of the hydrogen blower 8. The condenser 6 condenses water vapor contained in the anode off-gas flowing through the hydrogen flow pipe L2 and other passages. The temperature raising unit 18 raises the temperature of the fuel electrode off-gas (produced hydrogen) between the condenser 6 and the hydrogen blowers 7 and 8 and the flow meters F7 and F8.

[0027] That is, in the water electrolysis apparatus 1, during operation of the water electrolysis module 2, anode off-gas containing hydrogen is supplied from the anode 20b of each unit cell of the water electrolysis cell stack 20 via the hydrogen flow pipes L2 and L7 and the recycle pipe L8 to the hydrogen blower 7 (inlet), the flow meter F7, and the flow meter F8 and the hydrogen blower 8 (inlet). The water vapor contained in the anode off-gas flowing through the hydrogen flow pipe L2 is condensed in the condenser 6. The anode off-gas (produced hydrogen) that has passed through the condenser 6 is heated by the heating unit 18 between the condenser 6, the flow meter F8, and the hydrogen blower 8. The hydrogen heated by the heating unit 18 is supplied by the hydrogen blower 7 to the combustor 26 of the water electrolysis module 2 as hydrogen for combustion, and is also supplied by the hydrogen blower 8 to the anode 20b of each unit cell of the water electrolysis cell stack 20 as hydrogen for preventing oxidation.

[0028] This prevents the anode off-gas (produced hydrogen) at a temperature equal to or lower than the dew-point temperature from being supplied from the recycle pipe L8 to the hydrogen blower 7 and the flow meter F7, thereby making it possible to prevent water vapor from condensing in the recycle pipe L8, the hydrogen blower 7, and the flow meter F7. Furthermore, by preventing the anode off-gas (produced hydrogen) at a temperature equal to or lower than the dew-point temperature from being supplied from the recycle pipe L8 to the flow meter F8 and the hydrogen blower 8, it is possible to prevent water vapor from condensing in the flow meter F8 and the hydrogen blower 8. As a result, in the water electrolysis device 1, it is possible to effectively prevent performance degradation and deterioration of the water electrolysis module 2, i.e., the hydrogen blowers 7 and 8 and the flow meters F7 and F8 that recirculate hydrogen generated at the anode 20b of each unit cell of the water electrolysis cell stack 20 to the water electrolysis cell stack 20 or the combustor 26 of the water electrolysis module 2.

[0029] The water electrolysis device 1 also includes a housing 10 that houses the water electrolysis module 2 (water electrolysis cell stack 20), hydrogen blowers 7, 8, hydrogen flow pipes L2, L7, cycle pipe L8, condenser 6, etc., and the temperature raising section 18 is formed by a part of the hydrogen flow pipe L7 and a part of the recycle pipe L8 that are arranged in an area around the ventilation fan 17 in the housing 10 where the temperature is higher than the dew point temperature of the anode off-gas (produced hydrogen) at the outlet of the condenser 6. This makes it possible to effectively use the heat released into the housing 10 when steam electrolysis is performed in the water electrolysis cell stack 20 to raise the temperature of the anode off-gas (produced hydrogen) supplied from the condenser 6 to the hydrogen blowers 7, 8, etc. As a result, additional installation of a heater or the like is unnecessary, making it possible to effectively prevent increases in the cost and power consumption of the water electrolysis device 1.

[0030] Furthermore, the housing 10 of the water electrolysis apparatus 1 includes an air inlet 13 for taking air into the interior and an exhaust duct 16 that forms an exhaust outlet 15 for discharging the internal air to the outside, and the temperature raising unit 18 is disposed inside the housing 10 so as to be closer to the exhaust outlet 15 than the air inlet 13. This makes it possible to effectively heat the anode off-gas (produced hydrogen) that is supplied from the condenser 6 to the hydrogen blowers 7, 8, etc., by the air that has absorbed heat from inside the housing 10.

[0031] The water electrolysis apparatus 1 also includes a ventilation fan 17 that sends air inside the casing 10 to the exhaust port 15. The air intake 13 is disposed in the lower part of the casing 10, and the exhaust port 15 is disposed in the upper part of the casing 10. The heating unit 18 is disposed inside the casing 10 so as to face the air inlet of the ventilation fan 17. This allows the air that has absorbed heat from inside the casing 10 to be efficiently collected in the heating unit 18, and enables the anode off-gas (produced hydrogen) that is supplied from the condenser 6 to the hydrogen blowers 7, 8, etc. to be effectively heated.

[0032] It should be noted that the invention of the present disclosure is not limited to the above-described embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above-described embodiment is merely one specific form of the invention described in the Summary of the Invention section, and does not limit the elements of the invention described in the Summary of the Invention section. [Industrial Applicability]

[0033] The presently disclosed invention is applicable to industries such as the manufacturing of water electrolysis devices. [Explanation of symbols]

[0034] 1 water electrolysis device, 2 water electrolysis module, 4 steam generator, 6 condenser, 7, 8 hydrogen blower, 10 housing, 13 air intake, 15 exhaust port, 17 ventilation fan, 18 heating section, 20 water electrolysis cell stack, 20b fuel electrode, F7, F8 flow meters, L2 hydrogen flow pipe, L7 hydrogen flow pipe (recycle passage), L8 recycle pipe (recycle passage).

Claims

1. A water electrolysis device including a water electrolysis module for generating hydrogen by steam electrolysis, a blower for supplying hydrogen to the water electrolysis module; a recycle passage for supplying hydrogen generated in the water electrolysis module from the water electrolysis module to an inlet of the blower; a condenser for condensing water vapor contained in the generated hydrogen; a temperature raising unit that raises the temperature of the produced hydrogen between the condenser and the blower;

2. The water electrolysis apparatus according to claim 1, a housing that houses the water electrolysis module, the blower, the recycle passage, and the condenser; the temperature raising section is formed by a part of the recycle passage disposed in a region within the housing where the temperature is higher than the dew point temperature of the produced hydrogen at the outlet of the condenser.

3. The water electrolysis apparatus according to claim 2, the housing includes an air intake port for taking in air into the interior and an exhaust port for discharging the air inside to the outside, The water electrolysis apparatus, wherein the temperature raising unit is disposed inside the housing so as to be closer to the exhaust port than the air intake port.

4. The water electrolysis apparatus according to claim 3, The air conditioner further includes a ventilation fan that sends air from inside the housing to the exhaust port, The air intake is disposed in a lower portion of the housing, the exhaust port is disposed in an upper portion of the housing, The water electrolysis apparatus, wherein the temperature raising unit is disposed in the housing so as to face an air inlet of the ventilation fan.

Images