JP4872204B2 - Reformer for hydrogen production - Google Patents

Description

  The present invention relates to a reformer for hydrogen production.

It is required that the component (reformer member) of a reformer for hydrogen production (hereinafter also simply referred to as a reformer) be as thin as possible in order to ensure a large heat transfer capacity. However, as the thickness of such components increases, the characteristics are reduced due to repeated peeling of the scale due to oxidation, and the service life is shortened. Against this background, SUS304 and SUS316L stainless steels have been conventionally used for such reformer members, and when these materials have insufficient durability, SUS310S and the ferrite system described in Patent Document 1 are used. Stainless steel is used.
Japanese Patent No. 2642056

  However, the above SUS304 and SUS316L (austenitic stainless steel) have a difficulty in use at high temperatures because the scale is spalled (peeled) and the plate thickness is greatly reduced. Further, in a high temperature atmosphere to which water vapor is added, the same phenomenon occurs even in SUS310S having a high material grade and ferritic stainless steel described in Patent Document 1 among austenitic stainless steels. Further, the reformer has a problem in that a temperature difference is generated between parts during operation, a thermal strain is generated due to the temperature difference, and a crack is generated. In this respect, austenitic stainless steel has a high coefficient of thermal expansion, which is disadvantageous for cracking.

  Accordingly, an object of the present invention is to provide a reformer for hydrogen production using a ferritic stainless steel which is unlikely to cause corrosion or thinning due to high temperature oxidation in a high temperature of 400 ° C. or higher or further in a steam addition atmosphere.

The present invention that has achieved the above object is as follows : ( 1 ) Al: 1.0 to 8.0 mass in a reformer member that includes a portion that forms a dense alumina coating at a use temperature of 400 ° C. or higher and that contacts a steam-containing gas. % And La: a reformer for producing hydrogen characterized by using ferritic stainless steel containing 0.010 to 0.150 mass%, and ( 2 ) a use temperature of 550 ° C. or higher. Ferritic stainless steel containing Al: 1.0 to 8.0 mass% and La: 0.010 to 0.150 mass% in a reformer member that includes a portion that forms a dense alumina coating and is in contact with a steam-containing gas This is a reformer for hydrogen production, characterized by comprising steel.

  According to the present invention, hydrogen is composed of a member that does not collapse due to abnormal oxidation and does not cause cracking due to thermal stress even when exposed to a water vapor-containing gas in a high temperature environment of 400 ° C. or higher, further 550 ° C. or higher. A production reformer is obtained.

  In the reformer for hydrogen production according to the present invention, the reformer member including the portion where the operating temperature is 400 ° C. or more is ferritic stainless steel containing Al: 1.0 to 8.0 mass%. It is necessary that a component other than Al may be added in an appropriate amount within a range not departing from the ferritic stainless steel. For example, it is a ferritic stainless steel specified in JIS G 4304 and 4305. For example, an appropriate amount of La may be added to improve the adhesion of the oxide film. The La addition amount is preferably 0.010 mass% or more and 0.150 mass% or less from the viewpoint of adhesion. In particular, when the ferritic stainless steel having the above composition is used for a constituent member having a portion where the operating temperature is 550 ° C. or higher or a portion in contact with the water vapor-containing gas, the effect of the present invention (when other materials are used) The difference in the effect) appears more prominently. The water vapor-containing gas here refers to a mixed gas of water (including natural gas or city gas) mainly composed of hydrocarbon gas such as methane and propane, and water vapor. Further, from the viewpoint of increasing the amount of oxidation, Al is preferably 3.0 mass% or more.

  20 mass% Cr-5 mass% Al (-0.080 mass% La added) ferritic stainless steel (referred to as steel A for the present invention), SUS304, SUS316L and SUS310S (the latter three are all less than Al: 1.0 mass%) FIG. 2 shows the oxidation resistance of the surface of each material when the steel plate samples were subjected to an oxidation test in a water vapor atmosphere at 900 ° C.-30 vol.%. The progress of oxidation was evaluated by oxidation increase. As the oxidation progresses, the steel is combined with oxygen and the weight increases. Therefore, the oxidation resistance of the material and the member can be evaluated by increasing the amount of oxidation. It turns out that steel A for this invention shows the oxidation resistance which was outstandingly excellent.

Moreover, when the surface layer part of the material subjected to the oxidation test at 1100 ° C. × 300 h was examined with a microscope, the steel A for the present invention formed a dense alumina (Al ₂ O ₃ ) film to suppress oxidation (see FIG. 3). On the other hand, even in SUS310S, which is excellent in heat resistance among austenite series, the grain boundaries were eroded and the scale was peeled off (see FIG. 4).

The reason why the amount of Al in the steel for use in the present invention is 1.0 to 8.0 mass% is that if it is less than 1.0 mass%, a dense alumina coating is not formed, and a (FeCr) ₂ O coating is formed to sufficiently oxidize. On the other hand, if it exceeds 8.0 mass%, the toughness of the hot-rolled sheet is remarkably lowered (see FIG. 6) and cannot be passed through the production line.

In the general polymer electrolyte fuel cell (PEFC) 1 shown in FIG. 1, the steel A plate (minimum plate) of the present invention is used as a component of the reformer 2 at least a part of which is 400 ° C. or higher when used. Thickness = 0.4 mm, maximum plate thickness = 3.0 mm) was used as an example of the present invention. The operating conditions of this reformer are: city gas composition = 20 vol. % Water vapor-CH ₄ —H ₂ —CO—CO ₂ , city gas supply flow rate = 0.8 m ³ (standard state) / h, exhaust gas composition = 25 vol. % Was steam _{-CO 2 -O} 2 -N 2. Also, it can be applied to a member having a thickness of 50 μm, 100 μm, or the like.

  As Comparative Examples 1 to 3, SUS304 (18Cr-0.002Al), SUS316L (17Cr-0.005Al), and SUS310S (24Cr-0.010Al) are used instead of the steel A for the present invention in the above-described inventive examples. A reformer configured in the same manner except that it was used was operated under the same conditions as in the above-described example of the present invention.

  As a result, as shown in FIG. 2, the life of the reformer was 600 h, 900 h, and 1500 h in Comparative Example 1 (SUS304), 2 (SUS316L), and 3 (SUS310S), respectively, whereas 40000 h in the present invention example. We were able to extend to.

  The same effect can be obtained when the present invention is applied to a reformer of a solid oxide fuel cell (SOFC).

  The present invention can be used for manufacturing a fuel cell.

It is sectional drawing which shows the outline | summary of the polymer electrolyte fuel cell (PEFC) for general households. Various stainless steels at 900 ° C.-30 vol. It is a graph which shows the relationship between the oxidation time in% water vapor | steam atmosphere, and oxidation increase. (A) shows a scanning cross-sectional photomicrograph of the microstructure of the steel A for the present invention after the 1100 ° C. × 300 h high temperature steam oxidation test, and (b), (c), (d) respectively It is EPMA density | concentration distribution map of O, C, and Al of (a). It is an optical microscope photograph copy figure of the microstructure which shows the sample section observation result after 1100 ° C x300h high temperature steam oxidation test of SUS310S. It is a schematic diagram which shows the relationship between Al content of a ferritic stainless steel, and a scale composition. 0.01 mass% C-20 mass% Cr-xmass% Al (x = 3,4,5,6,7,9) containing ferritic stainless steel hot rolled sheet (plate thickness 2.5 mm) temperature of Charpy impact value It is a graph which shows dependence.

Explanation of symbols

1 PEFC for general household
2 Reformer (reformer for hydrogen production)
3 Power generation parts

Claims (2)

  A reformer member including a portion that forms a dense alumina coating at a use temperature of 400 ° C. or more and is in contact with a water vapor-containing gas is Al: 1.0 to 8.0 mass% and La: 0.010 to 0.150 mass%. A reformer for producing hydrogen, characterized in that it is made of a ferritic stainless steel containing iron. Al: 1.0 to 8.0 mass% and La: 0.010 to 0.150 mass% for the reformer member that includes a portion that forms a dense alumina coating at a use temperature of 550 ° C. or higher and is in contact with the steam-containing gas. A reformer for producing hydrogen, characterized in that it is made of a ferritic stainless steel containing iron.

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