JP2011168862A - Water electrolysis system and method for operating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly improve system efficiency by effectively reducing energy loss. <P>SOLUTION: A water electrolysis system 10 includes: a water electrolysis apparatus 14 electrolyzing water and generating hydrogen and oxygen; a cooler 20 connected to the downstream side of a hydrogen passage 16 discharging the hydrogen from the water electrolysis apparatus 14 and cooling the discharged hydrogen; a water adsorption tube 22 adsorbing water in the cooled hydrogen; a back pressure regulating valve 24 located downstream from the water adsorption tube 22 and maintaining the hydrogen discharged from the hydrogen passage 16 at a pressure higher than an atmospheric pressure; and a gas-liquid separator 18 located between the water electrolysis apparatus 14 and the cooler 20 and exchanging heat between the hydrogen released from the back pressure regulating valve 24 and the hydrogen discharged from the water electrolysis apparatus 14. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a water electrolysis system and an operation method thereof for electrolyzing water by energization from a DC power source to generate oxygen and hydrogen at a pressure higher than normal pressure, and to dehumidify the high-pressure hydrogen.

  For example, in a polymer electrolyte fuel cell, a fuel gas (a gas containing mainly hydrogen, such as hydrogen gas) is supplied to the anode side electrode, while an oxidant gas (mainly containing oxygen) is supplied to the cathode side electrode. By supplying a gas (for example, air), direct current electric energy is obtained.

  In general, a water electrolysis apparatus is employed to produce hydrogen gas that is a fuel gas. This water electrolysis apparatus uses a solid polymer electrolyte membrane (ion exchange membrane) in order to decompose water and generate hydrogen (and oxygen). Electrode catalyst layers are provided on both sides of the solid polymer electrolyte membrane to form an electrolyte membrane / electrode structure, and a power feeder is provided on both sides of the electrolyte membrane / electrode structure. It is configured. That is, the unit is configured substantially in the same manner as the above fuel cell.

  Therefore, in a state where a plurality of units are stacked, a voltage is applied to both ends in the stacking direction, and water is supplied to the anode-side power feeding body. For this reason, water is decomposed and hydrogen ions (protons) are generated on the anode side of the electrolyte membrane / electrode structure, and the hydrogen ions permeate the solid polymer electrolyte membrane and move to the cathode side to bond with electrons. Thus, hydrogen is produced. On the other hand, on the anode side, oxygen produced together with hydrogen is discharged from the unit with excess water.

  Since this type of water electrolysis system generates high-pressure hydrogen of several tens of MPa, for example, a high-pressure hydrogen production method and production apparatus disclosed in Patent Document 1 are known. As shown in FIG. 7, the high-pressure hydrogen production apparatus includes an oxygen high-pressure vessel 1, a differential pressure adjustment device 2, a hydrogen high-pressure vessel 3, an electrolysis cell 4, a moisture adsorption cylinder 5, a back pressure valve 6, a hydrogen cooler 7, and a deoxygenation cylinder. 8 is provided.

  The pure water in the oxygen high-pressure vessel 1 is sent to the anode side of the electrolytic cell 4 through a circulation pump, and the pure water is electrolyzed by energizing the electrolytic cell 4 from a power source. Oxygen generated in the electrolysis cell 4 by this electrolysis is sent to the oxygen high-pressure vessel 1 together with the circulating water returning pure water of the circulation pump.

  Hydrogen generated at the cathode of the electrolytic cell 4 is released into the hydrogen high-pressure vessel 3 together with the permeated water. At that time, the pressure in the oxygen high-pressure vessel 1 and the pressure in the hydrogen high-pressure vessel 3 are made equal by the differential pressure adjusting device 2.

  The hydrogen stored in the hydrogen high-pressure vessel 3 is cooled by the hydrogen cooler 7 after the oxygen contained in the hydrogen is removed through the deoxygenation cylinder 8 to condense moisture above the dew point temperature. Further, the dehumidified hydrogen is removed from the moisture adsorption cylinder 5 connected to the back pressure valve 6 to obtain product hydrogen.

JP 2007-100204 A

  By the way, in said patent document 1, in order to dehumidify high pressure hydrogen, the hydrogen cooler 7 is used. For example, a Peltier element is used as the hydrogen cooler 7. The high-pressure hydrogen obtained from the hydrogen high-pressure vessel 3 is cooled and dehumidified by energizing the Peltier element. Therefore, there is a problem that power is constantly consumed for the dehumidifying process, and the system efficiency is lowered.

  Moreover, in the back pressure valve 6, the set pressure is higher than the pressure at the supply destination of the high-pressure hydrogen. As a result, the high-pressure hydrogen released from the back pressure valve 6 is radiated by the reduced pressure, but the energy generated by this radiating cannot be used effectively. For this reason, there exists a problem that system efficiency falls.

  An object of the present invention is to solve this type of problem, and to provide a water electrolysis system capable of effectively reducing energy loss and reliably improving system efficiency, and an operation method thereof. To do.

  The water electrolysis system according to the present invention is connected to a water electrolysis device that electrolyzes water by energization from a DC power source to generate hydrogen and oxygen, and a hydrogen discharge port that discharges the hydrogen from the water electrolysis device. A cooling device that cools the discharged hydrogen, a water adsorption device that adsorbs the water in the cooled hydrogen, and the hydrogen that is disposed downstream of the water adsorption device and is discharged from the hydrogen discharge port. Is maintained between a pressure regulating valve that maintains a pressure higher than normal pressure, the water electrolysis device and the cooling device, and the hydrogen discharged from the pressure regulation valve and the water electrolysis device are discharged from the water electrolysis device. And a heat exchange device that exchanges heat with hydrogen.

  The operation method according to the present invention includes a step of starting the water electrolysis device, a step of detecting a hydrogen temperature between at least the heat exchange device and the pressure regulating valve, and cooling based on the detected hydrogen temperature. And operating the device.

  Further, this operation method calculates a temperature difference between the detected hydrogen temperature before the heat exchange and the detected hydrogen temperature before the heat exchange between the water electrolysis apparatus and the heat exchange apparatus. And a step of operating the cooling device when the calculated temperature difference is equal to or less than a set value.

  Furthermore, in this operation method, it is preferable to stop the heat exchange process by the heat exchange device when operating the cooling device.

  According to the present invention, the heat exchange device disposed between the water electrolysis device and the cooling device includes hydrogen released from the pressure regulating valve, that is, hydrogen that has been depressurized and reduced in temperature, and the water electrolysis device. Heat exchange is performed with the high-pressure hydrogen discharged.

  Accordingly, high-pressure hydrogen is dehumidified using hydrogen released from the pressure regulating valve as a cooling medium, and it is not necessary to energize the electric cooling device. As a result, energy loss can be effectively reduced, and system efficiency can be reliably improved.

  Further, according to the present invention, at least the hydrogen temperature between the heat exchange device and the pressure regulating valve is detected, and the cooling device is operated based on the detected hydrogen temperature. For this reason, the dehumidification treatment of the high-pressure hydrogen discharged from the water electrolysis apparatus is performed efficiently and reliably.

It is a schematic structure explanatory view of a water electrolysis system concerning a 1st embodiment of the present invention. It is a flowchart explaining the operating method of the said water electrolysis system. It is explanatory drawing of each detection temperature and hydrogen filling pressure in the said water electrolysis system. It is operation | movement explanatory drawing of the said water electrolysis system. It is a schematic structure explanatory drawing of the water electrolysis system concerning a 2nd embodiment of the present invention. It is a flowchart explaining the operating method of the said water electrolysis system. 1 is a schematic explanatory diagram of a high-pressure hydrogen production apparatus disclosed in Patent Document 1. FIG.

  As shown in FIG. 1, the water electrolysis system 10 according to the first embodiment of the present invention is supplied with pure water generated from city water via a pure water supply device 12, and electrolyzes the pure water. A water electrolysis device 14 for producing hydrogen, and a gas-liquid separator (heat exchange device) 18 for removing water contained in the high-pressure hydrogen led out from the water electrolysis device 14 to the hydrogen lead-out path 16 by heat exchange. A cooler (for example, a Peltier element) (cooling device) 20 that cools the hydrogen discharged from the gas-liquid separator 18, and moisture contained in the cooled hydrogen discharged from the cooler 20. The water adsorbing cylinder (water adsorbing device) 22 to be removed and the hydrogen discharged from the hydrogen lead-out path 16 are maintained at a pressure higher than normal pressure (for example, 35 MPa). Back pressure valve (pressure adjustment valve) 24 Equipped with a.

  In the water electrolysis apparatus 14, a plurality of water decomposition cells 26 are stacked, and end plates 28 a and 28 b are disposed at both ends of the water decomposition cell 26 in the stacking direction. The water electrolysis device 14 is connected to an electrolysis power source 30 that is a DC power source. The anode (anode) of the water electrolysis device 14 is connected to the positive electrode of the electrolysis power supply 30, while the cathode (cathode) is connected to the negative electrode of the electrolysis power supply 30.

  A pipe 32a is connected to the end plate 28a, and pipes 32b and 32c are connected to the end plate 28b. The pipes 32 a and 32 b circulate pure water from the pure water supply device 12 via the water pump 36 disposed in the circulation path 34, while the pipe 32 c serving as a hydrogen discharge port passes through the hydrogen lead-out path 16. Connected to the gas-liquid separator 18.

  The hydrogen lead-out path 16 is located between the gas-liquid separator 18 and the back pressure valve 24, more specifically, located between the cooler 20 and the water adsorption cylinder 22, and detects the hydrogen temperature. A temperature sensor 38 is arranged for this purpose. A detection signal from the temperature sensor 38 is sent to the controller 40. The temperature sensor 38 may be disposed between the gas-liquid separator 18 and the cooler 20.

  The water adsorbing cylinder 22 includes an adsorption tower (not shown) filled with a moisture adsorbing material that adsorbs water vapor (moisture) contained in hydrogen by physical adsorption and discharges moisture to the outside. A dry hydrogen supply path 42 is connected to the downstream side (outlet side) of the water adsorption cylinder 22 via a back pressure valve 24. Instead of the back pressure valve 24, various valves such as a solenoid valve may be used.

  The dry hydrogen supply path 42 is freely connectable to a heat exchange supply path 46 and a bypass path 48 via a three-way valve 44. The heat exchange supply path 46 is piped into the gas-liquid separator 18 and communicates with the heat exchange discharge path 50. The bypass path 48 is connected in the middle of the heat exchange discharge path 50 and is connected as a hydrogen supply path 52 to a hydrogen tank 54 capable of storing hydrogen (dry hydrogen).

  The hydrogen tank 54 is provided with an on-off valve 56 and can be connected to a fuel tank (not shown) of the fuel cell vehicle 58. Note that the hydrogen tank 54 may be provided as necessary, and the hydrogen tank 54 may be deleted.

  The operation of the water electrolysis system 10 configured as described above will be described below along the flowchart shown in FIG. 2 in relation to the operation method according to the first embodiment.

  First, when the water electrolysis system 10 is started (activated) (step S1), pure water generated from city water is supplied to the water electrolysis device 14 via the pure water supply device 12. In the water electrolysis apparatus 14, when energized from the electrolysis power supply 30, pure water is electrolyzed and generation of hydrogen is started.

  Hydrogen generated in the water electrolysis device 14 is sent to the gas-liquid separator 18 through the hydrogen lead-out path 16. In the gas-liquid separator 18, as will be described later, water vapor contained in hydrogen is separated from the hydrogen by heat exchange. The hydrogen from which the water vapor has been removed passes through the cooler 20 and is sent to the water adsorption cylinder 22.

  In the water adsorption cylinder 22, water vapor contained in hydrogen is adsorbed to obtain dry hydrogen (dry hydrogen). A back pressure valve 24 is disposed downstream of the water adsorption cylinder 22. For this reason, hydrogen can be pressurized and held in the water adsorption cylinder 22 until the hydrogen pressure in the water adsorption cylinder 22 reaches the set pressure.

  When the hydrogen pressure in the water adsorption cylinder 22 reaches the set pressure, the back pressure valve 24 is opened, and dry hydrogen is led from the water adsorption cylinder 22 to the dry hydrogen supply path 42. This dry hydrogen is, for example, decompressed from 35 MPa to several MPa, and becomes low-temperature hydrogen by heat dissipation.

  The low-temperature dry hydrogen led out to the dry hydrogen supply path 42 is supplied to the heat exchange supply path 46 under the action of the three-way valve 44, and is introduced into the gas-liquid separator 18 through the heat exchange supply path 46. Accordingly, in the gas-liquid separator 18, heat exchange is performed between the low-temperature dry hydrogen and the high-temperature high-pressure hydrogen discharged from the water electrolysis device 14. Thereby, the high pressure hydrogen is cooled and dehumidified.

  On the other hand, the low-temperature dry hydrogen is sent from the heat exchange discharge path 50 to the hydrogen supply path 52 and stored in the hydrogen tank 54 after the heat exchange process. The dry hydrogen stored in the hydrogen tank 54 is filled into the fuel cell vehicle 58 under the opening action of the on-off valve 56 as necessary.

  In the controller 40, the temperature of the high-pressure hydrogen discharged from the gas-liquid separator 18 through the hydrogen lead-out path 16 is detected (step S2). FIG. 3 shows the relationship between the filling hydrogen pressure of the fuel cell vehicle 58 (or the hydrogen tank 54) and each detected temperature. In FIG. 3, line L1 is the temperature of high-pressure hydrogen discharged from the water electrolysis device 14, line L2 is the temperature of high-pressure hydrogen discharged from the cooler 20, and line L3 is the back pressure valve 24. Is the temperature of hydrogen released from.

  The high-pressure hydrogen discharged from the water electrolysis device 14 is maintained at a substantially constant temperature T0 ° C., and the temperature of the high-pressure hydrogen discharged from the gas-liquid separator 18 is that of the fuel cell vehicle 58 (or hydrogen tank 54). It gradually increases as the filling hydrogen pressure increases. This is because the hydrogen pressure difference before and after the back pressure valve 24 decreases.

  Next, in step S3, when the detected hydrogen temperature becomes equal to or higher than the set temperature T1 ° C. (YES in step S3), the process proceeds to step S4 and the cooler 20 is turned on. For this reason, the water | moisture content in the high voltage | pressure hydrogen sent with electricity to the cooler 20 and sent to the said cooler 20 is condensed, and it isolate | separates from hydrogen as condensed water.

  At that time, as shown in FIG. 4, the three-way valve 44 is switched, and the dry hydrogen supply path 42 is connected to the hydrogen supply path 52 via the bypass path 48. That is, dry hydrogen bypasses the gas-liquid separator 18. When the hydrogen filling process into the fuel cell vehicle 58 (or the hydrogen tank 54) is completed, the operation of the water electrolysis device 14 is stopped (YES in step S5).

  In this case, in the first embodiment, the gas-liquid separator 18 disposed between the water electrolysis device 14 and the cooler 20 is hydrogen released from the back pressure valve 24, that is, the pressure is reduced and the temperature is lowered. Heat exchange is performed between hydrogen and high-pressure hydrogen discharged from the water electrolysis apparatus 14.

  Accordingly, since the high-pressure hydrogen is dehumidified using the low-temperature (low-pressure) hydrogen released from the back pressure valve 24 as a cooling medium, it is not necessary to energize the cooler 20 that is an electric cooling device. Thereby, an energy loss can be reduced effectively and the effect that it becomes possible to improve the efficiency of the water electrolysis system 10 reliably is acquired.

  In the first embodiment, the temperature sensor 38 detects the hydrogen temperature between the gas-liquid separator 18 and the back pressure valve 24, and the cooler 20 is operated based on the detected hydrogen temperature. . For this reason, there is an advantage that the dehumidification treatment of the high-pressure hydrogen discharged from the water electrolysis device 14 is performed efficiently and reliably.

  FIG. 5 is a schematic configuration explanatory view of a water electrolysis system 60 according to the second embodiment of the present invention. In addition, the same reference number is attached | subjected to the component same as the water electrolysis system 10 which concerns on 1st Embodiment, and the detailed description is abbreviate | omitted.

  In the water electrolysis system 60, a first temperature sensor 38 a is disposed between the water electrolysis device 14 and the gas-liquid separator 18, and a second temperature sensor is disposed between the cooler 20 and the water adsorption cylinder 22. 38b is disposed.

  The operation of the water electrolysis system 60 configured as described above will be described below along the flowchart shown in FIG. 6 in relation to the operation method according to the second embodiment.

  When the water electrolysis system 10 is started (step S11), the process proceeds to step S12, and the temperature of the high-pressure hydrogen discharged from the water electrolysis device 14 (hereinafter referred to as the first hydrogen temperature) is detected by the first temperature sensor 38a. At the same time, the temperature of the high-pressure hydrogen discharged from the gas-liquid separator 18 and the cooler 20 (hereinafter referred to as the second hydrogen temperature) is detected by the second temperature sensor 38b.

  In the controller 40, a temperature difference between the first hydrogen temperature and the second hydrogen temperature is calculated (step S13). Then, it is determined whether or not the calculated temperature difference is equal to or less than a predetermined value (for example, 10 ° C.) set in advance (step S14).

  When it is determined that the calculated temperature difference is equal to or less than the predetermined value (YES in step S14), the process proceeds to step S15, and the cooler 20 is turned on. For this reason, the water | moisture content in the high voltage | pressure hydrogen sent with electricity to the cooler 20 and sent to the said cooler 20 is condensed, and it isolate | separates from hydrogen as condensed water. Furthermore, when the hydrogen filling process to the fuel cell vehicle 58 is completed, the operation of the water electrolysis device 14 is stopped (YES in step S16).

  As described above, in the second embodiment, heat exchange is performed between the hydrogen released from the back pressure valve 24 and the high-pressure hydrogen discharged from the water electrolysis device 14, so that the efficiency of the water electrolysis system 60 is improved. The same effects as those of the first embodiment can be obtained, for example, it is possible to improve the reliability.

DESCRIPTION OF SYMBOLS 10, 60 ... Water electrolysis system 12 ... Pure water supply apparatus 14 ... Water electrolysis apparatus 16 ... Hydrogen lead-out path 18 ... Liquid separator 20 ... Cooler 22 ... Water adsorption cylinder 24 ... Back pressure valve 26 ... Water decomposition cell 30 ... Electrolysis Power supply 38 ... Temperature sensor 40 ... Controller 42 ... Dry hydrogen supply path 44 ... Three-way valve 52 ... Hydrogen supply path 54 ... Hydrogen tank 58 ... Fuel cell vehicle

Claims (4)

A water electrolysis device that electrolyzes water by energization from a DC power source to generate hydrogen and oxygen;
A cooling device that is connected downstream of a hydrogen discharge port that discharges the hydrogen from the water electrolysis device and cools the discharged hydrogen;
A water adsorption device for adsorbing water in the cooled hydrogen;
A pressure regulating valve disposed downstream of the water adsorbing device and maintaining the hydrogen discharged from the hydrogen discharge port at a pressure higher than normal pressure;
A heat exchange device that is disposed between the water electrolysis device and the cooling device and performs heat exchange between the hydrogen discharged from the pressure control valve and the hydrogen discharged from the water electrolysis device;
A water electrolysis system comprising: A water electrolysis device that electrolyzes water by energization from a DC power source to generate hydrogen and oxygen;
A cooling device that is connected downstream of a hydrogen discharge port that discharges the hydrogen from the water electrolysis device and cools the discharged hydrogen;
A water adsorption device for adsorbing water in the cooled hydrogen;
A pressure regulating valve disposed downstream of the water adsorbing device and maintaining the hydrogen discharged from the hydrogen discharge port at a pressure higher than normal pressure;
A heat exchange device that is disposed between the water electrolysis device and the cooling device and performs heat exchange between the hydrogen discharged from the pressure control valve and the hydrogen discharged from the water electrolysis device;
A method for operating a water electrolysis system comprising:
Starting the water electrolysis device;
Detecting a hydrogen temperature at least between the heat exchange device and the pressure regulating valve;
Operating the cooling device based on the detected hydrogen temperature;
A method for operating a water electrolysis system, comprising: The operation method according to claim 2, wherein a step of detecting a hydrogen temperature before heat exchange between the water electrolysis device and the heat exchange device;
Calculating a temperature difference between the detected pre-heat exchange hydrogen temperature and the detected hydrogen temperature;
When the calculated temperature difference is equal to or less than a set value, and operating the cooling device;
A method for operating a water electrolysis system, comprising:   4. The operation method according to claim 2, wherein when the cooling device is operated, the heat exchange process by the heat exchange device is stopped.

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