JP4987375B2 - Hydrogen production system and method - Google Patents

Description

  The present invention relates to a hydrogen production system and method for suppressing permeation of tritium in hydrogen production.

  Currently, hydrogen is produced using fossil resources as energy sources or using fossil resources as raw materials. This contradicts the concept of introducing hydrogen energy, which is the use of environmentally friendly energy that does not emit carbon dioxide. In order to resolve this contradiction, it is necessary to produce using only natural energy or nuclear energy as an energy source and water as a raw material.

  As one of the methods, hydrogen production using nuclear energy is attracting attention, and hydrogen production using a HTTR is the most promising production method (for example, patents). Reference 1).

This hydrogen production (steam reforming method) system using HTTR includes a high temperature gas reactor (HTTR) and a hydrogen production system. The heat discharged from the HTGR is exchanged with the secondary helium gas via the intermediate heat exchanger and used as a heat source for methane steam reforming reaction, steam production, and the like. The steam reforming reaction in the hydrogen production system is performed in a steam reformer. A secondary helium gas flows outside the reaction tube of the steam reformer, and a process gas consisting of a raw material gas and a product gas flows inside, and heat is supplied from the secondary helium gas to produce hydrogen.
JP 2005-289740 A

  In any case regarding hydrogen production using the heat of the nuclear power plant described above, it is necessary to handle tritium, which is an isotope of hydrogen. This tritium is a radioactive element, and there is a concern about the influence on the human body. Therefore, it is necessary to confine the tritium in the plant without discharging it as much as possible.

  However, since this tritium has a permeation characteristic, tritium may pass through inside and outside the heat transfer tube of the intermediate heat exchanger and the catalyst tube of the steam reformer, and may be mixed into the produced hydrogen. Since these devices require strength, workability, and corrosion resistance, it is desirable to use a metal material. However, since metal promotes the transmission of tritium, it is necessary to take measures to reduce the transmission. There was a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a hydrogen production system and method for suppressing diffusion of tritium in a steam reforming reaction and preventing permeation of tritium. .

In order to achieve the above object, in the hydrogen production system of the present invention, hydrogen is produced using a heat exchanger that performs heat exchange of heat supplied from a nuclear power plant, and heat that is exchanged by the heat exchanger. An internal structure that contacts the heat exchanger or a coolant containing tritium in the steam reformer, and the inner layer and the outer layer combine two or more materials having different crystal structures. It is produced using the metal material material produced in this way.

In order to achieve the above object, in the hydrogen production method of the present invention, a heat exchange step of exchanging heat supplied from a nuclear power plant using a heat exchange heat exchanger, and heat exchange using the heat exchanger are performed. and heat by using and a steam production step for producing hydrogen by using a steam reformer, a metal material member inner and outer layers are fabricated in combination of two or more materials having different crystal structures A tritium permeation suppression step of suppressing the permeation of tritium by flowing a fluid containing tritium in the internal structure of the heat exchanger or steam reformer manufactured in the above. is there.

According to the hydrogen production system and the method of the present invention, the inner layer and the outer layer have a crystal structure with respect to piping that may permeate tritium, utilizing the fact that diffusion of hydrogen in a metal material is lattice diffusion. By combining different metal material materials , tritium diffusion can be suppressed and tritium permeation can be prevented.

  Embodiments of a hydrogen production system and method according to the present invention will be described below with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

  FIG. 1 is a configuration diagram showing a schematic configuration of a hydrogen production system 4 using a HTGR 2, FIG. 2 is a longitudinal sectional view showing a configuration of the steam reformer 6 in FIG. 1, and FIG. FIG. 2 is a longitudinal sectional view showing the configuration of the intermediate heat exchanger 3 in FIG. 1.

  FIG. 1 is a configuration diagram showing an outline of a hydrogen production system 4 using a high-temperature gas reactor (HTTR) 2 according to a first embodiment of the present invention. As shown in this figure, the part surrounded by the dotted line is the nuclear power plant 1, and the part surrounded by the solid line is the hydrogen production system 4.

  In this nuclear power plant 1, as an example, primary helium gas 2 a having a temperature of about 950 ° C. from a high temperature gas reactor (HTTR) 2 is used as a heating source. The primary helium gas 2a is led to the intermediate heat exchanger 3 which is a heat exchanger, exchanges heat with the secondary helium gas 4a sent from the hydrogen production system 4, and is warmed. The helium gas 4a is led out to the steam reformer 6 via the high temperature isolation valve 5 as it is. Thus, the heat supplied from the HTGR 2 is exchanged with the secondary helium gas 4a through the intermediate heat exchanger 3, and used as a heat source for methane steam reforming reaction, steam production, etc. Is done.

  The steam reforming reaction in the hydrogen production system 4 is performed in the steam reformer 6. A raw material gas 41 a such as methane is introduced from the raw material gas storage tank 41 through the heat exchanger 42 into the steam reformer 6. Further, water 7 a is supplied from the steam generator 7 via the heat exchanger 43. In the steam reformer 6, the raw material gas 41a and the water 7a are heated by the secondary helium gas 4a introduced and heated via the secondary helium gas system 8, and the hydrogen 6a is produced. . The hydrogen 6 a produced here is supplied to the hydrogen storage tank 44 via the heat exchanger 42. The primary helium gas 2a discharged from the high temperature gas furnace 2 includes tritium 45 generated by neutron irradiation in the high temperature gas furnace 2.

  2A and 2B are explanatory views of the embodiment of the steam reformer of FIG. 1, wherein FIG. 2A is a longitudinal sectional view thereof, and FIG.

  As shown in the figure, a plurality of helium flow pipes 10 in which the secondary helium gas 4a flows and contacts are suspended in the steam reformer 6. Tritium 45 is contained in the secondary helium gas 4a. Inside the helium channel tube 10, a reaction tube 11 (thick line portion) into which a source gas 41a that is an internal structure flows is inserted. In addition, inside the reaction tube 11, a bayonet inner tube 12 through which the generated hydrogen 6a flows out is accommodated.

  A high-temperature secondary helium gas 4 a is introduced from the lower part 61 of the steam reformer 6. The introduced secondary helium gas 4 a exchanges heat by flowing while in contact with the helium passage tube 10, and flows out through the pipe 62 at the intermediate portion of the steam reformer 6.

  As described above, the helium channel tube 10 is heated by the secondary helium gas 4a. By this heating, in the reaction tube 11 accommodated in the helium flow channel tube 10, the raw material gas 41a and the water vapor react to produce hydrogen 6a. The produced hydrogen 6a is collected via the bayonet inner tube 12.

  In the present embodiment configured as described above, in the steam reformer 6, the water 7a that has passed through the raw material gas 41a and the steam generator 7 (shown in FIG. 1) is sent, and the heat of the secondary helium gas 4a. With this, hydrogen production is performed and hydrogen is supplied. That is, in the steam reformer 9, the secondary helium gas 4a flows outside the reaction tube 12, and the process gas consisting of the raw material gas 41a and the product gas flows inside the reaction tube 12 which is an internal structure. Heat is supplied from the secondary helium 4a to produce hydrogen 6a. The technology related to this reaction can also be applied to a reactor of an IS process which is a different hydrogen production method.

  Next, a schematic structure of the intermediate heat exchanger 3 is shown in FIG.

  As shown in the figure, the secondary system helium gas 4a is supplied to the central portion of the intermediate heat exchanger 3 through the secondary system helium gas flow path 14 which is an internal structure. On the other hand, the high-temperature primary system helium gas 2 a is supplied to the inner wall side of the intermediate heat exchanger 3 from the lower part 63 and the intermediate part 64 of the intermediate heat exchanger 3 via the primary system helium gas flow path 15. . The high-temperature primary helium gas 2a flows on the inner wall side and contacts the secondary helium gas 4a through the partition wall to exchange heat.

  In the present embodiment configured as above, the secondary helium gas flow path 14 in the intermediate heat exchanger 3 is provided on the inner side, and the primary helium gas flow path 15 is provided on the outer side. Through the heat exchange. At this time, the probability that the tritium 45 contained in the primary helium gas 2a is transferred to the secondary helium gas 4a is the highest. In response to this, the internal structure (thick line portion) constituting the secondary system helium gas flow path 14 is formed of a constituent material produced by combining two or more types of metal materials having different crystal structures. Alternatively, it is formed using a metal material to which an oxide film is attached.

  According to the present embodiment, the effect of suppressing the migration of tritium can be obtained as described later by using a constituent material produced by combining two or more metal materials having different crystal structures. As this material, stainless steel, nickel base alloy, Ti alloy and molybdenum are used.

  FIG. 4 is an explanatory diagram of the location of hydrogen 50 due to the difference in crystal structure. (A) is the location of hydrogen 50 in the face-centered cubic lattice (fcc), and (b) is the hydrogen in the body-centered cubic lattice (bcc). 50 positions are shown.

  As shown in this figure, the hydrogen 50 (● mark) in the metal material exists at the position of the interstitial space 52 formed by the metal atom 51 (◯ mark), but is not stationary and always moves through the interstitial space 52. is doing. 4A shows the structure of fcc, which is a face-centered cubic lattice, and FIG. 4B shows the structure of bcc, which is a body-centered cubic lattice. As shown in this figure, the position of hydrogen 50 differs depending on the crystal lattice. Since this hydrogen 50 moves between the lattices 52, if the materials of different lattices are combined, the movement of the lattices 52 becomes difficult, and if the distance between the lattices 52 becomes longer, the activation energy value necessary for the movement becomes higher. As a result, the diffusion rate of hydrogen 50 decreases. Therefore, if metal materials having different crystal structures are used in combination, diffusion of hydrogen 50, that is, diffusion of tritium 45 can be suppressed. Since tritium 45 is an isotope of hydrogen 50 and has the same characteristics, if the behavior of hydrogen 50 can be suppressed, the behavior of tritium 45 can also be suppressed.

  According to the present embodiment, stainless steel and nickel-based alloy have a body-centered cubic (fcc) structure, and molybdenum has a face-centered cubic (bcc) structure. The oxide film mainly composed of Fe, Ni and Cr has a trigonal or cubic structure. By combining two or more materials and oxide films having different crystal structures, hydrogen diffusion can be suppressed.

  FIG. 5 is an explanatory view of another embodiment of the intermediate heat exchanger 3 of FIG.

  As shown in the figure, molybdenum is disposed on the inner layer 16 of the internal structure (thick line portion) 14a constituting the secondary system helium gas flow path 14, and stainless steel is disposed on the outer layer 17 for bonding.

  In the present embodiment configured as described above, materials having different crystal structures are arranged.

It is formed from a component produced by combining two or more metal materials having different crystal structures. Alternatively, it is formed using a metal material to which an oxide film is attached.

  According to the present embodiment, by utilizing the fact that diffusion of hydrogen 50 in the metal is lattice diffusion, by combining materials having different crystal structures or oxide films with respect to piping that may permeate tritium 45, , Diffusion of tritium 45 can be suppressed, and permeation of tritium 45 can be prevented. In this way, if materials having different crystal structures such as molybdenum are arranged on the inner layer 16 of the internal structure (thick line portion) constituting the secondary helium gas flow path 14 and stainless steel is arranged on the outer layer 17 and bonded together, , It becomes difficult for hydrogen to move from molybdenum to stainless steel, so it is difficult to diffuse to the outside.

  As this metal material, molybdenum may be disposed on the inner layer 16 and a nickel-based alloy may be disposed on the outer layer 17. The same effect can be obtained also when the inner layer 16 is made of stainless steel or a nickel base alloy and the outer layer 17 is an oxide film mainly composed of Fe, Cr or Ni.

  FIG. 6 is an explanatory view of still another embodiment of the intermediate heat exchanger of FIG. 1, wherein (a) is a longitudinal sectional view thereof, and (b) is an enlarged sectional view of a C portion thereof.

  As shown in the figure, the structure (bold line portion) 14 a constituting the secondary helium gas flow path 14 has a three-layer structure of an inner layer 16, an inner layer 18 and an outer layer 17. Stainless steel is disposed on the inner layer 16, molybdenum is disposed on the inner layer 18, and a nickel-based alloy is disposed on the outer layer 17.

  According to the present embodiment, hydrogen diffusion can be further suppressed by adopting a three-layer structure such as stainless steel for the inner layer 16, molybdenum for the inner layer 18 and nickel-based alloy for the outer layer 17. . Furthermore, the strength as a structural material can be improved.

  Instead of the three-layer structure formed from the stainless steel, molybdenum and nickel-based alloy, the three-layer structure may be a three-layer structure of stainless steel, molybdenum and nickel-based alloy from the inner layer toward the outer layer. Similar effects can be obtained.

  Moreover, as a modification of this structural material, from the inner layer to the outer layer, a three-layer structure of stainless steel, molybdenum and stainless steel, a nickel-based alloy, a three-layer structure of molybdenum and nickel-based alloy, molybdenum, stainless steel and molybdenum And a three-layer structure of molybdenum, a nickel-based alloy, and molybdenum can be listed.

  Furthermore, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention by combining the embodiments of the present invention. it can.

The block diagram which shows schematic structure of the hydrogen production system using a high temperature gas furnace. It is explanatory drawing of embodiment of the steam reformer of FIG. 1, (a) is the longitudinal cross-sectional view, (b) is the A section expanded sectional view. The longitudinal cross-sectional view which shows the structure of embodiment of the intermediate heat exchanger of FIG. FIG. 3 is an explanatory diagram of hydrogen existing positions depending on crystal structures, where (a) shows the hydrogen existing positions in the face-centered cubic lattice (fcc), and (b) shows the hydrogen existing positions in the body-centered cubic lattice (bcc). FIG. It is explanatory drawing of other embodiment of the intermediate heat exchanger of FIG. 1, (a) is the longitudinal cross-sectional view, (b) is the B section expanded sectional view. It is explanatory drawing of other embodiment of the intermediate heat exchanger of FIG. 1, (a) is the longitudinal cross-sectional view, (b) is the C section expanded sectional view.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Nuclear power plant, 2 ... High temperature gas reactor, 2a ... Primary helium gas, 3 ... Intermediate heat exchanger, 4 ... Hydrogen production system, 4a ... Secondary helium gas, 5 ... High temperature isolation valve, 6 ... Steam reform Gasifier, 6a, 50 ... Hydrogen, 7 ... Steam generator, 8 ... Secondary helium gas system, 9 ... Steam reformer, 10 ... Helium channel tube, 11 ... Reaction tube, 12 ... Bionic net tube, DESCRIPTION OF SYMBOLS 14 ... Secondary system helium gas flow path, 15 ... Primary system helium gas flow path, 16 ... Inner layer, 17 ... Outer layer, 18 ... Middle layer, 41 ... Source gas storage tank, 41a ... Source gas, 42, 43 ... heat exchanger, 44 ... hydrogen storage tank, 45 ... tritium, 51 ... metal atom, 52 ... interstitial.

Claims (5)

A heat exchanger for exchanging heat supplied from a nuclear power plant,
A steam reformer that produces hydrogen using the heat exchanged in this heat exchanger;
With
Internals in contact with coolant containing tritium in the heat exchanger or steam reformer, using a metal material member inner and outer layers are fabricated in combination of two or more materials having different crystal structures A hydrogen production system characterized by being produced.   The hydrogen production system according to claim 1, wherein the metal material is made of stainless steel, a nickel-base alloy, and molybdenum.   The hydrogen production system according to claim 1, wherein the metal material is made of a three-layer structure of stainless steel, molybdenum, and a nickel-based alloy.   2. The hydrogen production system according to claim 1, wherein the metal material is made of a three-layer structure formed of two kinds of materials selected from stainless steel, molybdenum and stainless steel. A heat exchanging step of exchanging heat supplied from the nuclear power plant using a heat exchanging heater;
  A steam production step for producing hydrogen using a steam reformer using the heat exchanged in this heat exchanger;
  With
  A fluid in which tritium is contained in the internal structure of a heat exchanger or steam reformer made using a metal material made by combining two or more materials having different crystal structures in the inner layer and the outer layer. A tritium permeation suppression step for suppressing the permeation of tritium by flowing;
  A method for producing hydrogen, comprising:

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