JPH06287002A - Device for reforming fuel - Google Patents

Abstract

(57) [Summary] [Objective] In a reformer having a honeycomb catalyst, the temperature drop in the catalyst is suppressed by improving the method of supplying heat to the inside of the catalyst while taking advantage of the low pressure loss. A highly reactive fuel reformer is provided. [Structure] A flat honeycomb catalyst 1 is provided in a square tubular reaction tube 20 having a flat cross section which constitutes a fuel reformer 10.
1 and the heater 30 is in close contact with the reaction tube 20 so as to cover the entire outer peripheral surface of the reaction tube 20. The honeycomb catalyst 11 has a lateral cross-sectional aspect ratio of 3. The main components of the raw material gas are methane and water vapor, and they are introduced into the reaction tube 20 through the suction pipe 21.
The reaction tube 20 is heated by the heater 30. The raw material gas causes a chemical reaction while passing through the Hanimuka hole 12 formed in the honeycomb-shaped catalyst 11 in the reaction tube 20, and becomes a hydrogen-rich reformed gas. The reformed gas is sent from the exhaust pipe 22 to a CO shift converter (not shown).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel reformer for producing hydrogen, and more particularly to the structure of a fuel reformer.

[0002]

2. Description of the Related Art In thermal power generation, nuclear power generation, etc., electric energy is obtained after converting chemical energy of fossil fuel into heat energy or nuclear energy, whereas a fuel cell directly obtains electric energy from chemical energy. This fuel cell is a chemical cell in which reactants are continuously supplied from the outside, and a fuel cell main body, a fuel reformer, and a power converter are main constituent elements, and a control device is added to these constituent elements. A fuel cell system is constructed by adding an exhaust heat recovery device.

Of these, the fuel reforming apparatus is an apparatus for reforming a raw material gas containing a fuel gas such as methane and steam as main components into a hydrogen-rich reformed gas. The raw material gas is mixed with hydrogen and carbon dioxide gas. It is composed of a reformer for converting carbon oxides and a CO shifter for converting carbon monoxide in the reformed gas to an allowable concentration or less. Known catalysts for the reformer include pellet catalysts and honeycomb catalysts.

In the reformer, when the raw material gas passes through the catalyst layer filled in the reaction tube, the raw material gas is reformed and CO
Supplied to the transformer. At this time, since it is the steam reforming method, the reforming reaction in the reaction tube is promoted by being heated by the heater, and the raw material gas is converted into the reformed gas containing hydrogen, carbon dioxide gas and carbon monoxide. .

[0005]

However, since the reforming reaction is an endothermic reaction, in the conventional fuel reforming apparatus, a large temperature drop occurs in the catalyst during the progress of the reaction, and the reactivity also drops accordingly. This phenomenon becomes a particularly important problem in the honeycomb-shaped catalyst, which is generally said to have poor thermal conductivity from the circumferential portion toward the center, and the heat is not sufficiently supplied from the outer wall surface of the reaction tube. Has the problem that the temperature required for the reaction cannot be achieved in the center of the catalyst. On the other hand, a pellet-shaped catalyst having better thermal conductivity than a honeycomb-shaped catalyst has a problem that reduction in pressure loss cannot be expected.

Further, since the raw material gas that has entered the vicinity of the reaction tube of the honeycomb-shaped catalyst and the raw material gas that has entered the central portion do not switch to the outlet of the reaction tube, the raw material gas that passes through the lower temperature central portion has the target reaction rate However, there is a problem that the overall efficiency is reduced. The present invention has been made to solve such a problem, and in a reformer having a honeycomb catalyst, improves the method of supplying heat to the inside of the catalyst while taking advantage of the low pressure loss. In this way, it is an object of the present invention to provide a highly reactive fuel reforming device that suppresses the temperature drop in the catalyst.

[0007]

Therefore, in the fuel reforming apparatus of the present invention, there is provided a reaction tube through which a raw material gas flows, and a flat tube which is housed in the reaction tube and has a short heat transfer distance from the outer peripheral portion to the central portion. The honeycomb-shaped catalyst and the heater for heating the reaction tube from the outside are provided.

In the structure of the fuel reformer, it is desirable that the honeycomb catalyst has a cross-sectional aspect ratio b / a of 3 or more.

[0009]

According to the fuel reforming apparatus of the present invention, since the honeycomb catalyst is flat, the thermal conductivity is good, and the heating of the reaction tube by the heater alleviates the temperature drop in the catalyst due to the endothermic reaction.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 of the present invention is shown in FIGS. 1, 2 and 3. The fuel reforming device 10 mainly reforms the fuel gas and steam in the raw material gas. This fuel reformer 10
The honeycomb-shaped catalyst 11 is filled in the rectangular tube-shaped reaction tube 20 constituting the above, and the heater 30 is in close contact so as to cover the entire outer peripheral surface of the reaction tube 20.

As shown in FIG. 2, the honeycomb catalyst 11 has a cross-sectional aspect ratio b / a of 3, and as shown in FIG. 3, cordierite honeycomb catalyst carrier 15 forming honeycomb holes 12. Alumina layer 13 is coated on the inner wall surface 15a, and a nickel layer 14 is carried thereon by an impregnation method. The reaction tube 20 is formed of stainless steel having a rectangular tubular shape.

The heater 30 is an inner surface combustion type burner. The main components of the raw material gas are methane and water vapor, and they are introduced into the reaction tube 20 through the suction pipe 21. The heater 30 is shown in Table 1.
Under the conditions of 1100 ± 50 ° C.
Heat to. The raw material gas causes a chemical reaction represented by the following formula (1) while passing through the Hanimuka hole 12 formed in the honeycomb catalyst 11. Since this chemical reaction is an endothermic reaction,
The temperature of the honeycomb catalyst 11 is lowered.

CH ₄ + H ₂ O → CO + 3H ₂ (endothermic reaction) (1)

[0014]

[Table 1]

Since the honeycomb catalyst 11 is flat as shown in FIG. 2, the heat conducting surface of the honeycomb catalyst 11 is increased and the heat transfer distance in the longitudinal direction of the cross section is shortened. When 20 is heated, heat is rapidly transferred to the central portion of the honeycomb catalyst 11, and the temperature decrease inside the honeycomb catalyst 11 is relieved. Therefore, the fuel reforming reaction of the raw material gas represented by the formula (1) proceeds favorably. The reformed gas is sent from the exhaust pipe 22 to a CO shift converter (not shown).

In order to unify the reaction rate evaluation criteria in the measurement of the reaction rate of the fuel reforming reaction when the cross-sectional shape and the cross-section aspect ratio b / a of the honeycomb-shaped catalyst shown in Table 2 are unified, The catalyst occupancy volume supported on the carrier is fixed at 5 ×
It was set to 10 ^-3 m ³ . The heat transfer surface area represents the side area of the outer periphery of the honeycomb-shaped catalyst, and changes depending on the shape of the cross-section of the honeycomb-shaped catalyst and the cross-section lateral / aspect ratio b / a.

[0017]

[Table 2]

As shown in Table 2, as compared with Comparative Example 1 using a conventional cylindrical honeycomb catalyst, Comparative Examples 2 and 3 in which the cross-sectional aspect ratio b / a of the honeycomb catalyst is less than 3. The reaction rate of the fuel reforming reaction of Example 1 is remarkably high. Further, since the honeycomb catalyst 11 is flat, the reformer 10 as a whole is flat, and it is possible to install the reformer 10 in a space that could not be installed conventionally. Further, as shown in FIGS. 4, 5 and 6, the shape and arrangement of the honeycomb holes 12 of the honeycomb catalyst 11 of Example 1 can be changed to honeycomb holes 12a, 12b and 12c.

Examples 2 and 3 of the present invention are shown in Table 2
As shown in FIG. 7, the honeycomb catalyst 11 of Example 1 has a cross-sectional aspect ratio b / a of 4 in Example 2 and 5 in Example 3, and other configurations and operations are the same as those of Example 1. Is the same. As the cross-section aspect ratio b / a increases, the reaction rate of the fuel reforming reaction also increases. Example 4 of the present invention is shown in FIG.

In Example 4, three reaction tubes 20 and four heaters 40 are alternately stacked in layers. Heat insulation container 5
0 covers the entire surfaces of the reaction tube 20 and the heater 40. The heater 40 is an outer surface combustion type burner. The source gas is
It is introduced from the suction pipe 21 into each of the three reaction tubes 20 by a distribution pipe 23. The reformed source gas is fed from the collecting pipe 24,
It is sent to a CO transformer (not shown).

Example 4 has a laminated structure in which three reaction tubes 20 and four heaters 40 are alternately stacked in layers.
Since the honeycomb-shaped catalyst 11 is flat, the reaction tubes 20 are flat, and stacking is easy, and a stacked structure can be formed without taking up space. In addition, since the number of reaction tubes per fuel reformer is larger than in Examples 1, 2 and 3, a large amount of reformed gas can be produced by increasing the inflow amount of the raw material gas. The numbers of the reaction tubes 20 and the heaters 40 are not limited to the numbers realized in the fourth embodiment.

A fifth embodiment of the present invention is shown in FIG. Example 5
Is a heater 30 for heating the reaction tube 20 as in Example 1.
The reaction tube 20 is in contact with the fuel cell 60. In this embodiment, the fuel cell 60, which replaces the heater, supplies the heat necessary for reforming the raw material gas to the reaction tube 20. A shown in FIG.
The source gas introduced into the reaction tube 20 from the direction is heated and reformed by the heat generated from the fuel cell 60 to become a reformed gas. The reformed gas is made to have a carbon monoxide concentration not higher than an allowable concentration by the CO shift converter 50, and is sent to the fuel cell 60. The fuel cell 60 sends the generated direct current to a current converter (not shown).

In the fifth embodiment, as a means for heating the reaction tube 20, instead of the heater 30 of the first embodiment, a fuel cell 60 is used.
Since the space for the heater is not needed, the miniaturization of the system can be promoted by eliminating the heater. As a means for heating, other heat generating portion in the system may be used instead of the fuel cell 60 as long as the required heat can be supplied to the reaction tube 20.

[0024]

As described above, according to the fuel reforming apparatus of the present invention, the honeycomb catalyst is flattened to improve the thermal conductivity of the honeycomb catalyst, thereby suppressing the temperature drop in the catalyst layer. Further, there is an effect that the temperature distribution of the raw material gas can be made uniform and the reactivity of reforming the raw material gas can be improved.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a fuel reformer according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged view of a dotted line III portion in FIG.

[Fig. 4] Fig. 4 is a cross-sectional view of a honeycomb-shaped catalyst of Example 1 in which the shape and arrangement of the honeycomb holes are changed.

FIG. 5 is a cross-sectional view of a honeycomb-shaped catalyst of Example 1 in which the shape and arrangement of the honeycomb holes are changed.

[Fig. 6] Fig. 6 is a cross-sectional view of a honeycomb-shaped catalyst of Example 1 in which the shape and arrangement of honeycomb holes are changed.

FIG. 7 is a schematic vertical sectional view of a fuel reformer according to a fourth embodiment of the present invention.

FIG. 8 is a schematic diagram of a fuel reformer and a fuel cell according to a fifth embodiment of the present invention.

[Explanation of symbols]

 10 Fuel reforming apparatus 11 Honeycomb catalyst 12 Honeycomb hole 20 Reaction tube 30 Heater 40 Heater 50 CO shifter 60 Fuel cell 70 Fuel system

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hidenobu Misawa 1-1 Nishidaine, Sakae-cho, Toyoake-shi, Aichi Prefecture 50 (72) Inventor Yukio Nagasaka 5 at 16 East Higashi, Tozaki-cho, Okazaki-shi, Aichi Prefecture

Claims (2)

[Claims] 1. A reaction tube for flowing a raw material gas, a flat honeycomb catalyst housed in the reaction tube and having a short heat transfer distance from an outer peripheral portion to a central portion, and heating for heating the reaction tube from the outside. And a fuel reformer. 2. A cross-sectional aspect ratio of the honeycomb-shaped catalyst, b /
The fuel reformer according to claim 1, wherein a is 3 or more.