JP2008223107A - System and method for electrolyzing high temperature steam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems: conventional electrolysis of high temperature steam requires the separation of hydrogen and steam because hydrogen-enriched steam and high temperature pure oxygen are generated and the recovery of the oxygen is difficult in the conventional electrolysis of high temperature steam. <P>SOLUTION: A steam electrolyzing apparatus 10 is constituted of a hydrogen pole chamber 11 having a hydrogen pole 14, an oxygen pole chamber 12 having an oxygen pole 15, and a proton-conductive solid electrolyte 13. Water supplied from a water supply part 1 is converted into high temperature steam in a temperature raising part 2, and the high temperature steam is supplied to the oxygen pole chamber 12. An electric power is supplied to the steam electrolyzing apparatus 10 from a power source 5, and steam electrolysis is performed in the apparatus 10. Hydrogen gas is generated in the hydrogen pole chamber 11, and oxygen-enriched steam wherein oxygen and high temperature steam are mixed is generated in the oxygen pole chamber 12. Since hydrogen and the oxygen-enriched steam are generated, the separation of hydrogen and steam is not required, and the reduction of partial pressure of oxygen is not required. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high temperature steam electrolysis system and a high temperature steam electrolysis method.

A conventionally known high-temperature steam electrolysis method performs electrolysis by supplying high-temperature steam to an electrolysis cell using an oxygen ion conductive solid electrolyte. When high-temperature steam is introduced into a hydrogen electrode chamber having a hydrogen electrode, H ₂ O + 2e ⁻ → H ₂ + O ²⁻ (1), which is a hydrogen electrode electrolysis reaction
The high temperature steam is decomposed and hydrogen and oxygen ions are generated. The generated oxygen ions move to the oxygen electrode chamber having the oxygen electrode through the oxygen ion conductive solid electrolyte. ^{_{O 2- → 1 / 2O 2 +}} 2e oxygen electrode electrolysis reaction at the oxygen electrode chamber - (2)
As a result, oxygen and electrons are generated, and the electrons move to the hydrogen electrode chamber via an external circuit. Hydrogen generated in the hydrogen electrode chamber is discharged from the hydrogen electrode chamber as hydrogen-enriched water vapor mixed with high-temperature water vapor, and oxygen is discharged from the oxygen electrode chamber.

As such a high-temperature steam electrolysis method, hydrogen enriched with hydrogen extracted from a high-temperature steam electrolysis cell by supplying air and steam heated by a heating source to a high-temperature steam electrolysis apparatus using an oxygen ion conductive solid electrolyte and performing electrolysis at a high temperature. There is one that recovers hydrogen from hydrogenated steam (see, for example, Patent Document 1).
JP-A-6-93481

  In the conventional high-temperature steam electrolysis apparatus, hydrogen is discharged as hydrogen-enriched steam, and thus a process for separating hydrogen and steam is necessary. In addition, pure oxygen is generated in the conventional high-temperature steam electrolysis apparatus, but since high-temperature pure oxygen has high reactivity, a process for reducing the oxygen partial pressure by supplying air to the generated oxygen is required. .

  The present invention has been made to solve the above-described problems, and includes a high-temperature steam electrolysis system and a high-temperature steam electrolysis method that can eliminate the process of separating hydrogen and steam and the process of reducing the partial pressure of generated oxygen. The purpose is to provide.

  In order to achieve the above-described object, a high-temperature steam electrolysis system according to the present invention includes a water supply unit, a temperature raising unit that heats water supplied from the water supply unit to form high-temperature steam, a container, A proton conductive solid electrolyte that is formed as a partition wall and does not transmit gas that forms an oxygen electrode chamber and a hydrogen electrode chamber; a porous hydrogen electrode formed on a surface of the proton conductive solid electrolyte in contact with the hydrogen electrode chamber; A porous oxygen electrode formed on a surface of the proton conductive solid electrolyte in contact with the oxygen electrode chamber; and electrolyzing high-temperature steam supplied from the temperature raising unit to the oxygen electrode chamber; A steam electrolyzer that discharges oxygen-enriched water vapor from the chamber and hydrogen from the hydrogen electrode chamber; a power source that supplies power to the water vapor electrolyzer; and the oxygen-enriched water vapor discharged from the oxygen electrode chamber as a refrigerant And heat exchange Allowed, characterized in that it comprises a condenser for discharging the oxygen-enriched water vapor as the oxygen and condensed water.

  Further, the high temperature steam electrolysis method according to the present invention comprises a proton conductive solid electrolyte impermeable to separation gas which is formed as a partition in a container and forms an oxygen electrode chamber and a hydrogen electrode chamber, and the hydrogen electrode chamber of the proton conductive solid electrolyte. Power is supplied to a water vapor electrolysis apparatus having a porous hydrogen electrode formed on a surface in contact with the oxygen electrode and a porous oxygen electrode formed on a surface in contact with the oxygen electrode chamber of the proton conductive solid electrolyte. Is heated to high temperature water vapor, and the high temperature water vapor is supplied to the oxygen electrode chamber to perform electrolysis to produce oxygen in the oxygen electrode chamber and hydrogen in the hydrogen electrode chamber, and oxygen enrichment from the oxygen electrode chamber Water vapor is discharged from the hydrogen electrode chamber, respectively, and the oxygen-enriched water vapor is heat-exchanged with a refrigerant to be separated into oxygen and condensed water.

  ADVANTAGE OF THE INVENTION According to this invention, the high temperature steam electrolysis system which can make the process of isolate | separating hydrogen and water vapor | steam and the process of reducing the partial pressure of produced | generated oxygen unnecessary can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 and 2 are block diagrams showing the configuration of a high-temperature steam electrolysis system according to Embodiment 1 of the present invention and a modification thereof.

  The configuration of the high-temperature steam electrolysis system according to this embodiment will be described below.

  The water supply unit 1 is connected to the temperature raising unit 2 through a pipe L1. The temperature raising unit 2 is connected to the oxygen electrode chamber 12 of the steam electrolysis apparatus 10 through a pipe L2 using the exhaust heat of the reactor as a heat source.

The water vapor electrolysis apparatus 10 includes a hydrogen electrode chamber 11 and an oxygen electrode chamber 12 formed by separating the inside of a container 16 with a gas-impermeable electrolyte 13, and the surface of the electrolyte 13 in contact with the hydrogen electrode chamber 11 is porous. A porous oxygen electrode 15 is provided on the surface of the electrolyte 13 in contact with the oxygen electrode chamber 12. The electrolyte 13 is a proton conductive solid electrolyte using BaCeO ₃ , SrCeO ₃ or the like. For the hydrogen electrode 14 and the oxygen electrode 15, for example, a porous body such as a nickel-based metal mixed with a proton conductive electrolyte is used.

  Further, the oxygen electrode 15 of the water vapor electrolysis apparatus 10 is connected to the positive electrode of the power source 5 via the electric wire E <b> 1, and the hydrogen electrode 14 is connected to the negative electrode of the power source 5 via the electric wire E <b> 2.

  The oxygen electrode chamber 12 is connected to the condenser 3 via a pipe L4.

  The condenser 3 is connected to a pipe L4 and a pipe L7. The condenser 3 is a heat exchanger that exchanges heat between the refrigerant in the pipe L7 and the fluid in the pipe L4. Water or the like is used as the refrigerant in the pipe L7. The pipe L4 is connected to the pipe L5 and the pipe L6 via the condenser 3.

  In addition, the hydrogen electrode chamber 11 of the steam electrolysis apparatus 10 is connected to the hydrogen treatment unit 4 via a pipe L3. The hydrogen processing unit 4 is a process that uses supplied hydrogen, such as a hydrogen storage process that stores hydrogen in a high-pressure hydrogen tank, a hydrogen storage alloy, or the like.

  Further, in the high-temperature steam electrolysis system according to the modification of the present embodiment shown in FIG. 2, the heat exchanger 8 that performs heat exchange between the fluid in the pipe L3 and the refrigerant in the pipe L8 is provided in the pipe L3. This is different from the first embodiment.

  The operation of the high-temperature steam electrolysis system according to this embodiment shown in FIG. 1 will be described below.

  The water supply unit 1 supplies water to the temperature raising unit 2 through the pipe L1. The temperature raising unit 2 raises the temperature of the supplied water to form high-temperature steam at about 600 ° C. or higher, and supplies it to the oxygen electrode chamber 12 of the water vapor electrolysis apparatus 10 via the pipe L2.

The high-temperature water vapor supplied to the oxygen electrode chamber 12 is subjected to an oxygen electrode electrolysis reaction at the oxygen electrode 15 H ₂ O → 2H ⁺ + 1 / 2O ₂ + 2e ⁻ (3)
Is decomposed into hydrogen ions, oxygen and electrons to generate oxygen. Hydrogen ions generated in the oxygen electrode chamber 12 move to the hydrogen electrode 14 via the proton conductive electrolyte 13 and electrons via the electric wire E1, the power source 5, and the electric wire E2. In the hydrogen electrode 14, hydrogen ions and electrons that have moved from the oxygen electrode chamber 12 are converted into hydrogen electrode reactions 2H ⁺ + 2e ⁻ → H _2. (4)
To hydrogen.

  Pure hydrogen generated in the hydrogen electrode chamber 11 is supplied to the hydrogen treatment unit 5 through the pipe L3.

  Oxygen generated in the oxygen electrode chamber 12 is mixed with high-temperature steam to become oxygen-enriched steam, and is introduced into the condenser 3 through the pipe L4. The oxygen-enriched water vapor introduced into the condenser 3 is cooled by exchanging heat with the refrigerant in the pipe L7, separated into oxygen and condensed water, oxygen is discharged from the pipe L5, and condensed water is discharged from the pipe L6. Thus, since the generated high-temperature oxygen is discharged as oxygen-enriched water vapor and then cooled and separated into oxygen and water, there is no need to lower the oxygen partial pressure.

  As shown in FIG. 2, the pipe L6 is connected to the pipe L1 connecting the water supply unit 1 and the temperature raising unit 2, and the condensed water discharged from the condenser 3 is introduced into the pipe L1 to perform high temperature steam electrolysis. It is also possible to use it.

  Further, the heat of the hydrogen in the pipe L3 can be recovered by the heat exchanger 8, and the heat recovered by the refrigerant in the pipe L8 is used as a heat engine such as a temperature rise of water in the pipe L1 or a Rankine cycle. Available to:

  According to the present embodiment, hydrogen gas and oxygen-enriched water vapor are generated by performing water vapor electrolysis in a high temperature water vapor electrolysis system configured using a water vapor electrolysis apparatus 10 having a proton conductive electrolyte 13, and hydrogen and water vapor are generated. The process of separating the gas and the process of reducing the partial pressure of the generated oxygen can be eliminated.

  FIG. 3 is a block diagram showing an outline of the high-temperature steam electrolysis system according to the second embodiment. In the high-temperature steam electrolysis system of this embodiment, a branch valve 21 provided in the middle of the pipe L3 as a hydrogen circulation means, a pipe L21 connecting the branch valve 21 and the hydrogen electrode chamber 11, and an oxygen-enriched steam circulation are provided. The difference from the first embodiment is that a branch valve 22 provided in the middle of the pipe L4 and a pipe L22 that connects the branch valve 22 to the pipe L2 are provided as means. In addition, the same code | symbol is attached | subjected to the structure same as Example 1, and the overlapping description is abbreviate | omitted.

  The branch valve 21 provided in the pipe L3 branches a part of the hydrogen discharged from the hydrogen electrode chamber 11 to the pipe L3 to the pipe L21, and the branched hydrogen is supplied to the hydrogen electrode chamber 11.

  Further, the branch valve 22 provided in the pipe L4 branches a part of the oxygen-enriched water vapor discharged from the oxygen electrode chamber 12 to the pipe L4 to the pipe L22. The high temperature steam branched into the pipe L22 is introduced into the pipe L2, and is supplied to the oxygen electrode chamber 12 together with the high temperature steam supplied from the temperature raising unit 2.

  The effect | action by a present Example is demonstrated below.

The steam electrolysis voltage E of the present embodiment can be calculated by the following equation using the Nernst equation.
E = E ₀ + (RT / 2F) × ln (P _H2 × P _O2 ^ 0.5) (5)

In order to use this equation, the hydrogen partial pressure P _H2 in the hydrogen electrode chamber 11 and the oxygen partial pressure P _O2 in the oxygen electrode chamber 12 are required, and are generated by high-temperature steam electrolysis in the hydrogen electrode chamber 11 and the oxygen electrode chamber 12. Since it is difficult to measure the partial pressure of hydrogen and the partial pressure of oxygen, it is difficult to calculate the electrolysis voltage. Therefore, the branch valves 21 and 22 are controlled so that a part of the hydrogen discharged from the hydrogen electrode chamber 11 is transferred to the hydrogen electrode chamber 11 and a part of the oxygen-enriched water vapor discharged from the oxygen electrode chamber 12 is transferred to the oxygen electrode chamber. 12 is introduced again to control the hydrogen partial pressure in the hydrogen electrode chamber 11 and the oxygen partial pressure in the oxygen electrode chamber 12, thereby stabilizing the electrolysis voltage.

  When the steam electrolysis operation of this system is stopped, all hydrogen is introduced into the pipe L21 and circulated in the branch valve 21, and all oxygen-enriched steam is introduced into the pipe L22 and circulated in the branch valve 22. Thus, the hydrogen electrode chamber 11 can be kept in a hydrogen atmosphere and the oxygen electrode chamber 12 can be kept in an oxygen atmosphere, and decomposition of the hydrogen electrode 14 and the oxygen electrode 15 can be prevented.

  According to the present embodiment, in addition to the effects of the first embodiment, the electrolysis voltage of water vapor can be stabilized by controlling the hydrogen partial pressure in the hydrogen electrode chamber 11 and the oxygen partial pressure in the oxygen electrode chamber 12.

  In addition, while the steam electrolysis operation is stopped, the hydrogen electrode chamber 11 and the oxygen electrode chamber 12 can be kept under a hydrogen atmosphere and an oxygen atmosphere, respectively, and decomposition of the hydrogen electrode 14 and the oxygen electrode 15 can be prevented.

  FIG. 4 is a block diagram showing an outline of the high-temperature steam electrolysis system according to the third embodiment. In addition, the same code | symbol is attached | subjected to the structure same as Example 1, and the overlapping description is abbreviate | omitted.

  The third embodiment shown in FIG. 4 is similar to the configuration of the first embodiment, but one end of the pipe L7 in the condenser 3 is connected to the water supply unit 1 and the other end is connected to the temperature raising unit 2. Water is used as the refrigerant in the pipe L7. Thus, the water from the water supply unit 1 in the pipe L7 is introduced into the temperature raising unit 2 after exchanging heat with the oxygen-enriched water vapor in the pipe L4 by the condenser 3. Thereby, the heat of the oxygen-enriched water vapor can be recovered and used for raising the temperature of the water.

  According to the present embodiment, in addition to the effects of the first embodiment, the heat of the oxygen-enriched steam discharged from the steam electrolysis apparatus 10 can be reused for steam electrolysis.

  As a modified example, instead of connecting the pipe L7 in the condensation period 3 and the water supply unit 1 as shown in FIG. 4, water as a refrigerant is not shown in the pipe L7 as shown in FIG. You may make it supply from a supply source.

  FIG. 6 is a block diagram showing a configuration of a high-temperature steam electrolysis system according to a fourth embodiment of the present invention. In this embodiment, the temperature of the water supplied from the water supply unit 1 is raised by the nuclear reactor 101, and the power is supplied to the steam electrolyzer 10 by generating power using the nuclear reactor 101 and the turbine 104. In addition, the same code | symbol is attached | subjected to the structure same as the Example mentioned above, and the overlapping description is abbreviate | omitted.

  Pipes L <b> 101 and L <b> 102 are introduced into the nuclear reactor 101, and the first heat medium and the second heat medium in the pipes L <b> 101 and L <b> 102 are heated by the nuclear reactor 101.

  The pipe L101 is formed as a closed loop in which a heat medium circulates through the nuclear reactor 101 and the heat exchanger 102. The heat exchanger 102 exchanges heat between the fluid in the pipe L1 and the heat medium in the pipe L101. The first heat medium is heated again in the nuclear reactor 101 after passing through the heat exchanger 102.

  The pipe L102 is formed as a closed loop in which a heat medium circulates through the nuclear reactor 101 and the heat exchanger 103. The heat exchanger 103 exchanges heat between the fluid in the pipe L103 and the second heat medium in the pipe L102. The second heat medium in the pipe L102 is heated in the nuclear reactor 101 again after heat exchange in the heat exchanger 103.

  The pipe L103 is formed as a closed loop in which the internal water passes through the heat exchanger 103, the turbine 104, and the condenser 106.

  A generator 105 is connected to the turbine 104, and the generator 105 generates power by the rotation of the turbine 104. The generator 105 is connected to the hydrogen electrode 14 and the oxygen electrode 15 of the steam electrolysis apparatus 10 via the electric wire E3, and is connected to a main transformer (not shown) via the electric wire E4.

  The operation of this embodiment will be described below.

  The nuclear reactor 101 raises the temperature of the first heat medium and the second heat medium in the pipes L101 and L102. The first heat medium in the pipe L101 is exchanged in the heat exchanger 102, and the second heat medium in the pipe L102 is again exchanged with the water in the pipes L1 and L103 in the heat exchanger 103, respectively. Heated in the reactor 101.

  The water in the pipe L103 is heated by heat exchange with the heat medium in the pipe L102 to become steam, supplied to the turbine 104, then condensed in the condenser 106, returned to water, and introduced again into the heat exchanger 103. Is done. The turbine 104 is rotated by receiving the supply of water vapor, whereby the generator 105 connected to the turbine 104 generates electric power, and the voltage is applied to the hydrogen electrode 14 and the oxygen electrode 15 of the water vapor electrolysis apparatus 10 via the electric wire E3. In addition, power is supplied to a main transformer (not shown) via the electric wire E4.

  The water supply unit 1 supplies water to the oxygen electrode chamber 12 of the steam electrolysis apparatus 10 through the pipe L101. The water in the pipe L1 is heat-exchanged with the heat medium in the pipe L101 by the heat exchanger 102 to form high-temperature steam, and then introduced into the oxygen electrode chamber 12.

  According to the present embodiment, in the high-temperature steam electrolysis system that uses the exhaust heat of the reactor as a power source for the high-temperature steam and the power source of the steam electrolysis apparatus, the process for separating hydrogen and steam and the partial pressure of the generated oxygen are reduced. Both processes can be made unnecessary.

  As mentioned above, although several Example was described about this invention, this invention is not limited to the said Example, A various deformation | transformation can be taken in the range which does not deviate from the meaning of invention. Those skilled in the art can make various modifications and changes in specific embodiments without departing from the technical idea and scope of the present invention. For example, it may be a configuration of a high temperature steam electrolysis system in which the features described in Examples 2 to 3 are arbitrarily combined.

The block diagram which shows the structure of the high temperature steam electrolysis system by Example 1 of this invention. The block diagram which shows the structure of the high temperature steam electrolysis system by the modification of Example 1 of this invention. The block diagram which shows the structure of the high temperature steam electrolysis system by Example 2 of this invention. The block diagram which shows the structure of the high temperature steam electrolysis system by Example 3 of this invention. The block diagram which shows the structure of the high temperature steam electrolysis system by the modification of Example 3 of this invention. The block diagram which shows the structure of the high temperature steam electrolysis system by Example 4 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water supply part 2 Temperature rising part 3 Condenser 4 Hydrogen processing part 5 Power supply 8, 102, 103 Heat exchanger 10 Steam electrolysis apparatus 11 Hydrogen electrode chamber 12 Oxygen electrode chamber 13 Electrolyte 14 Hydrogen electrode 15 Oxygen electrode 101 Reactor 104 Turbine 105 Generator 106 Condenser L1, L2, L3, L4, L5, L6, L7, L8, L21, L22, L101, L102, L103, L104 Piping E1, E2, E3, E4 Electric wire

Claims (8)

A water supply,
A temperature raising unit that heats water supplied from the water supply unit to form high-temperature steam;
A proton conductive solid electrolyte that is formed as a partition in the container and does not transmit gas that forms the oxygen electrode chamber and the hydrogen electrode chamber, and porous hydrogen formed on the surface of the proton conductive solid electrolyte in contact with the hydrogen electrode chamber An electrode, a porous oxygen electrode formed on a surface of the proton conductive solid electrolyte in contact with the oxygen electrode chamber, electrolyzing high-temperature steam supplied from the temperature raising unit to the oxygen electrode chamber, A steam electrolyzer that discharges oxygen-enriched water vapor from the oxygen electrode chamber and hydrogen from the hydrogen electrode chamber;
A power source for supplying power to the steam electrolyzer;
A heat exchanger for exchanging the oxygen-enriched water vapor discharged from the oxygen electrode chamber with a refrigerant, and discharging the oxygen-enriched water vapor as oxygen and condensed water;
A high-temperature steam electrolysis system comprising:   The high-temperature steam electrolysis system according to claim 1, further comprising condensed water supply means for supplying the condensed water discharged from the condenser to the temperature raising unit.   The high-temperature steam electrolysis system according to claim 1 or 2, further comprising a heat exchanger that exchanges heat between the hydrogen discharged from the hydrogen electrode chamber and a second refrigerant.   The oxygen-enriched water vapor circulation means for introducing at least a part of the oxygen-enriched water vapor discharged from the oxygen electrode chamber into the oxygen electrode chamber is provided. A high temperature steam electrolysis system as described in 1.   5. The high-temperature steam electrolysis according to claim 1, further comprising a hydrogen circulation unit that introduces at least part of the hydrogen discharged from the hydrogen electrode chamber into the hydrogen electrode chamber. system.   The said refrigerant | coolant is water, The water introduction means which introduces this water to the said temperature rising part after heat exchange with the said oxygen-enriched water vapor | steam is provided, The any one of Claims 1 thru | or 5 characterized by the above-mentioned. A high temperature steam electrolysis system as described in 1. A water supply,
A nuclear reactor for heating the first heating medium and the second heating medium;
A temperature raising means that heat-exchanges water supplied from the water supply unit with the first heat medium to form high-temperature steam;
A proton conductive solid electrolyte that is formed as a partition in the container and forms an oxygen electrode chamber and a hydrogen electrode chamber and is impermeable to separation gas, and a porous electrode formed on the surface of the proton conductive solid electrolyte in contact with the hydrogen electrode chamber. A hydrogen electrode, a porous oxygen electrode formed on a surface of the proton conductive solid electrolyte in contact with the oxygen electrode chamber, and electrolyzing high-temperature water vapor supplied from the temperature raising unit to the oxygen electrode chamber; A steam electrolyzer for discharging oxygen-enriched water vapor from the oxygen electrode chamber and hydrogen from the hydrogen electrode chamber,
A turbine to which water vapor generated by heat exchange between the second heat medium and water is supplied;
A generator driven by the turbine to supply power to the steam electrolyzer;
A heat exchanger for exchanging the oxygen-enriched water vapor discharged from the oxygen electrode chamber with a refrigerant, and discharging the oxygen-enriched water vapor as oxygen and condensed water;
A high-temperature steam electrolysis system comprising: A proton conductive solid electrolyte that is formed as a partition in the container and forms an oxygen electrode chamber and a hydrogen electrode chamber and is impermeable to separation gas, and a porous electrode formed on the surface of the proton conductive solid electrolyte in contact with the hydrogen electrode chamber. Supplying power to a water vapor electrolysis apparatus having a hydrogen electrode and a porous oxygen electrode formed on a surface of the proton conductive solid electrolyte in contact with the oxygen electrode chamber;
Heat the water to hot steam,
Electrolysis is performed by supplying the high temperature steam to the oxygen electrode chamber, oxygen is generated in the oxygen electrode chamber, and hydrogen is generated in the hydrogen electrode chamber,
Discharging oxygen-enriched water vapor from the oxygen electrode chamber and hydrogen from the hydrogen electrode chamber,
A high-temperature steam electrolysis method, wherein the oxygen-enriched water vapor is heat-exchanged with a refrigerant and separated into oxygen and condensed water.

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