JPH05301701A - Device for reforming fuel - Google Patents

Abstract

(57) [Abstract] [Purpose] Changes in the amount of combustion in the burner and the heat medium from the burner to the reaction tube having the catalyst layer in which the reforming catalyst is filled between the inner tube and the outer tube surrounding it. The uniform non-uniformity of the reformed gas composition in the radial direction caused by the non-uniform heating of the inner layer and the outer tube due to the non-uniform temperature distribution in the catalyst layer. [Composition] The heat medium from the burner flows down inside the inner tube of the reaction tube and then up the outer peripheral area of the outer tube, while the reforming raw material gas flows from the lower part to the upper part of the catalyst layer of the reaction tube. In a fuel reformer that reforms into a hydrogen-rich gas by a heat medium from a burner, the catalyst layer in the reaction tube is divided into two parts, and the reformed gas outlet side is made a catalyst layer having a larger heat capacity than the reforming raw material gas inlet side.
The catalyst layer having a large heat capacity is composed of a reforming catalyst in which the carrier supporting the catalyst has a large specific gravity.

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 reforming a raw fuel such as a hydrocarbon-based or alcohol-based fuel into a hydrogen-rich gas under a reforming catalyst, and more particularly, an on-state which is frequently started and stopped. The present invention relates to a fuel reformer incorporated in a site type fuel cell power generator.

[0002]

2. Description of the Related Art A fuel cell power generator is composed of a fuel reformer, a fuel cell main body, and auxiliary devices, and the hydrogen-rich reformed gas produced in the fuel reformer is supplied to the fuel cell as fuel. , Generates power by causing a battery reaction with the air supplied separately.

The reformed gas generated in the above fuel reformer is obtained by reforming a reforming raw material gas using hydrocarbon-based natural gas or alcohol-based methanol as a raw fuel under a reforming catalyst. can get. This reforming reaction is carried out by passing the raw fuel through a reaction tube having a catalyst layer filled with granular reforming catalyst in the fuel reformer, and when the raw fuel is methane, the following chemical formula 1, A few reactions are performed under a Ni-based catalyst at a reaction temperature of about 700 ° C.

[0004]

[Chemical Formula 1] CH ₄ + H ₂ O → CO + 3H ₂ H = -49.3 Kcal

[Chemical Formula 2] CO + H ₂ O → CO ₂ + H ₂ H = 9.8 Kcal

[Chemical Formula 3] CH ₄ + 2H ₂ O → CO ₂ + 4H ₂ H = -39.5 Kcal

When the raw fuel is methanol, the reactions of the following chemical formulas 4, 5, and 6 are carried out at a reaction temperature of about 200 to 300 ° C. using a Cu-based catalyst.

[0006]

[Chemical Formula 4] CH ₃ OH → 2H ₂ O + CO H = -21.7 Kcal

[Chemical Formula 5] CO + H ₂ O → CO ₂ + H ₂ H = 9.8 Kcal

[Chemical Formula 6] CH ₃ OH + H ₂ O → 3H ₂ + CO ₂ H = -11.9 Kcal

The steam reforming reaction in the catalyst layer of the fuel reformer for reforming the reforming raw material gas such as methane or methanol is an endothermic reaction and requires the supply of heat from the outside.

Further, hydrogen that has not been used for power generation in the fuel cell is recycled as off-gas to the burner of the fuel reformer and burned again, and is used as a heat source for heating the catalyst layer.

As a fuel reformer for carrying out such a steam reforming reaction, one shown in FIG. 3 is known. In FIG. 3, the furnace vessel 1 has a burner 2 in the center of the upper part and an exhaust gas outlet 3 for discharging combustion gas from combustion in the burner 2 to the upper part of the side wall.
And further includes a reforming tube 4 having a reaction tube 11.

The reforming tube 4 includes an inner tube 5 facing the burner 2 inside, an outer envelope 6 surrounding the burner 2, a bottom plate 7 closing the lower opening, an inner tube 5 and an outer envelope 6. The outer tube 8 is interposed between the outer tube 8 and the bottom plate 7. The annular space between the inner tube 5 and the outer tube 8 has a catalyst layer 10 filled with a reforming catalyst 9 therein, and the reaction is carried out. A tube 11 is formed. A reforming raw material gas passage 12 is provided between the outer tube 8 and the outer tube 6.

The upper openings of the outer tube 8 and the outer tube 6 of the reforming pipe 4 communicate with a reforming raw material gas manifold 13 provided in the upper part of the furnace vessel 1, and the reforming raw material gas manifold 13 is used as the reforming raw material. The reforming raw material gas inlet 14 into which the gas flows is provided. Further, the upper openings of the inner pipe 5 and the outer pipe 8 communicate with a reformed gas manifold 15 provided in the upper portion of the furnace vessel 1, and the reformed gas manifold 15 has a reformed gas outlet 16 for sending the reformed gas to the outside. I have it.

A combustion chamber 17 is formed inside the inner pipe 5, and a combustion gas passage 18 is formed between the outer pipe 6 and the side wall of the furnace vessel 1.

With this structure, when combustion is performed in the burner 2, the combustion gas flows downward in the combustion chamber 17 as indicated by the arrow, and returns at the lower end of the reforming pipe 4 to return to the combustion gas passage 18
And the reaction tube 11 is heated and then discharged from the exhaust gas outlet 3 to the outside.

On the other hand, the reforming raw material gas flows downward from the reforming raw material gas inlet 13 through the reforming raw material gas manifold 13 and into the catalyst layer 10 at the lower end thereof. Then, the reforming raw material gas flows from the lower part to the upper part through the catalyst layer 10 heated by the combustion gas, is steam-reformed by the catalytic action and is reformed into a hydrogen-rich gas, and passes through the reformed gas manifold 15. Reformed gas outlet 16
To the fuel cell.

[0015]

SUMMARY OF THE INVENTION The above fuel reformer is
Used for on-site fuel cell power generators. In this case, as a result of the heat cycle in which the fuel reformer is repeatedly started and stopped, the combustion amount of the burner of the fuel reformer changes,
The amount of heat transferred to the reaction tube changes, and the amount of heat transferred to the catalyst layer in the reaction tube changes frequently. In particular, the temperature of the combustion gas flowing in the combustion chamber 17 and the temperature of the gas passing through the combustion gas passage 18 are higher than the temperature of the combustion gas flowing in the combustion chamber 17. Therefore, in the catalyst layer in the reaction tube, the combustion chamber 17 side The temperature is high, the temperature is low on the combustion gas passage 18 side, and the temperature distribution is likely to occur in the catalyst layer, and the temperature distribution having a large temperature difference occurs in the radial direction.

For this reason, heat cannot be evenly transferred to the catalyst layer, and the reforming reaction cannot be performed well. For this reason, the composition of the reformed gas in the catalyst layer in the reaction tube tends to be unstable, like the temperature distribution. In particular, depending on the load fluctuation speed of the fuel cell, it is difficult to obtain a gas having a desired reformed gas composition even if the reformed gas amount can be supplied according to the load.

The object of the present invention is to improve the temperature distribution in the radial direction of the catalyst layer even if there is a change in the amount of combustion in the burner to the catalyst layer in the reaction tube or non-uniform heating of the inner and outer tubes by the combustion gas. It is an object of the present invention to provide a fuel reformer capable of obtaining a reformed gas having a uniform composition by reducing the temperature difference.

[0018]

In order to solve the above-mentioned problems, according to the present invention, an upright inner pipe and an outer pipe surrounding the upright inner pipe are provided, and an annular space between the inner pipe and the outer pipe is modified. A reaction tube having a catalyst layer filled with a high-quality catalyst, having a reforming source gas inlet at the lower end and a reforming gas outlet at the upper end,
A reactor vessel that has this reaction tube built-in and a burner that faces the upper inside of the inner tube of the reaction tube is provided.After flowing inside the inner tube, it is folded back at the lower end of the reaction tube and the outer peripheral area of the outer tube is provided. In the fuel reformer that heats the reaction tube with the heat medium generated by the combustion from the burner flowing through the reactor to reform the reforming raw material gas flowing from the inlet to the outlet into the hydrogen-rich gas, the catalyst layer is divided into two parts. The heat capacity of the catalyst layer on the outlet side of the reformed gas is larger than that on the inlet side of the reforming raw material gas.

The catalyst layer having a large heat capacity is composed of a reforming catalyst in which the carrier carrying the catalyst has a large specific gravity.

[0020]

The catalyst layer composed of the granular reforming catalyst in the upright reaction tube is divided into two, and the heat capacity of the catalyst layer on the outlet side of the reformed gas is made larger than that on the inlet side of the reforming raw material gas. As the specific gravity of the carrier supporting the catalyst is increased to increase the heat capacity, the change in the burner combustion amount due to the start and stop of the fuel reformer and the heat medium passing through the inner and outer tubes of the reaction tube Even if the amount of heat transferred into the catalyst layer changes due to the difference in the amount of heat transferred from the catalyst layer, if the catalyst layer on the outlet side of the reformed gas has a heat capacity of Since it is larger than the catalyst layer, it does not have a great influence on the temperature change of the catalyst layer.

Therefore, even if the composition of the reformed gas that is reformed by flowing through the catalyst layer composed of the ordinary granular reforming catalyst on the inlet side of the reforming raw material gas is not uniform in the radial direction, the reformed gas outlet Since the heat capacity of the catalyst layer on the side is large, the temperature difference in the temperature distribution in the radial direction becomes small, and the catalyst layer can maintain a sufficient temperature for reforming, so that the reforming reaction proceeds further and the reaction proceeds. When equilibrium is reached, the composition of the reformed gas at the outlet of the reaction tube is made uniform in the radial direction.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the same parts as those of the conventional example of FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. 1 is different from the conventional example in that the catalyst layer formed in the annular space between the inner pipe 5 and the outer pipe 8 is divided into two, and the heat capacity of the second catalyst layer 21 on the outlet side of the reformed gas above is divided. Is larger than that of the first catalyst layer 20 on the inlet side of the reforming raw material gas located below.

The formation of the catalyst layer having a large heat capacity is performed as follows. The α-alumina powder forming the carrier of the reforming catalyst is granulated by a granulator and baked to solidify to form a catalyst carrier having a large specific gravity. Α-Alumina powder was further granulated on the surface of the carrier to form a catalyst carrier composed of a porous body, and Ni was supported on the surface of the porous body to produce a reforming catalyst having a large heat capacity. The catalyst is filled to form the second catalyst layer 21.

With this structure, the reforming source gas passage 1
The reforming raw material gas passing through 2 flows from the inlet at the lower end of the reaction tube 11 into the first catalyst layer 20, and further flows into the second catalyst layer 21 having a large heat capacity. At this time, the combustion gas from the burner 2 flows downward in the combustion chamber 17 and then in the combustion gas passage 18 as described above, and the combustion gas causes the first and second catalyst layers 2 to
0 and 21 are heated and the reforming raw material gas undergoes a steam reforming reaction to be reformed into a hydrogen-rich gas. At this time, the composition of the reformed gas at the outlet of the first catalyst layer 20 on the inlet side of the reforming raw material gas is such that the change in the combustion amount in the burner 2 accompanying the start and stop of the fuel reformer and the temperature of the combustion gas are Since 17 is higher than the combustion gas passage 18, there is a non-uniform temperature distribution in the radial direction due to the difference in the amount of heat transfer from the combustion gas passing through the inner pipe and the outer pipe caused by the reformed gas composition. Is non-uniform. However, when the reformed gas having the non-uniform composition flows into the second catalyst layer 21 on the reformed gas outlet side, the second catalyst layer 21 has a high heat capacity, so that the temperature difference in the radial temperature distribution becomes small. Therefore, the steam reforming reaction further progresses in the second catalyst layer 21, and the reaction reaches equilibrium.

FIG. 2 shows the concentration distribution in the radial direction of the hydrogen gas concentration in the reformed gas at the catalyst layer outlet between the catalyst layer formation in the reaction tube according to the present invention and the conventional one.
The horizontal axis represents the radial position of the reaction tube, and the vertical axis represents the hydrogen gas concentration. In the figure, 25 shows the hydrogen concentration distribution in the radial direction of the reaction tube when the catalyst layer having a high heat capacity according to the present invention is provided and 24 is the conventional catalyst layer. From the figure, it is understood that the one according to the present invention has a smaller concentration difference in the hydrogen concentration distribution in the radial direction than the conventional one.

Although the reforming raw material gas passage 12 formed by the outer tube 8 of the reaction tube 11 and the outer envelope tube 6 is provided in this embodiment, the reforming raw material gas is not provided. Directly into the inner tube 5
The same effect can be obtained with a structure in which the reaction tube 11 including the outer tube 8 and the outer tube 8 is made to flow from the lower end to the upper end.

[0027]

As is apparent from the above description, according to the present invention, the catalyst layer of the reaction tube is divided into two parts, and the heat capacity of the catalyst layer on the reformed gas outlet side is made equal to that of the catalyst layer on the reformed raw material gas inlet side. By increasing the specific gravity of the carrier that supports the catalyst of the reforming catalyst and increasing the heat capacity as this means, the combustion amount changes in the burner and the heat passing through the inner and outer tubes of the reaction tube is increased. Even if there is a difference in the amount of heat transfer from the medium, the reformed gas exiting the catalyst layer on the inlet side of the reforming raw material gas and having a non-uniform composition in the radial direction will be generated in the catalyst layer with a high heat capacity on the outlet side of the reformed gas. The steam reforming reaction further proceeds to reach equilibrium, and a reformed gas having a uniform hydrogen gas concentration in the radial direction can be obtained at the catalyst layer outlet.

[Brief description of drawings]

1 is a partial cross-sectional view of a fuel reformer having a reaction tube according to an embodiment of the present invention.

FIG. 2 is a radial hydrogen concentration distribution map of the catalyst layer outlet in the reaction tube of the present invention and the conventional one.

FIG. 3 is a sectional view of a conventional fuel reformer.

[Explanation of symbols]

 1 Furnace Vessel 2 Burner 5 Inner Tube 8 Outer Tube 9 Reforming Catalyst 10 Catalyst Layer 11 Reaction Tube 17 Combustion Chamber 18 Combustion Gas Passage 20 First Catalyst Layer 21 Second Catalyst Layer

Claims (2)

[Claims] 1. A catalyst layer comprising an upright inner pipe and an outer pipe surrounding the upright inner pipe, the annular space between the inner pipe and the outer pipe being filled with a reforming catalyst, and the lower end portion being modified. The inlet of the quality source gas,
Further, provided with a reaction tube having an outlet for the reformed gas at the upper end and a reactor vessel having the burner facing the inner upper part of the inner tube of the reaction tube, after flowing inside the inner tube. , A hydrogen-rich reforming raw material gas that flows from the inlet to the outlet of the catalyst layer by heating the reaction tube with the heat medium generated by combustion from the burner that flows back at the lower end of the reaction tube and flows in the outer peripheral area of the outer tube In a fuel reformer that reforms into
A fuel reformer characterized in that the heat capacity of the catalyst layer on the outlet side of the reformed gas is larger than that on the inlet side of the reforming raw material gas. 2. The fuel reformer according to claim 1, wherein the catalyst layer having a large heat capacity comprises a reforming catalyst in which a carrier carrying the catalyst has a large specific gravity.