JP2938245B2 - Starting the fuel reformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for starting a fuel reformer for a fuel cell, which reforms a hydrocarbon-based raw fuel into a hydrogen-rich gas.

[0002]

A fuel cell power generation system is relatively compact and high efficiency, NO _X, there is almost no occurrence of SO _X.
Except for auxiliary equipment, there is no rotating equipment, so there is no noise and little vibration, and because of its excellent environmental adaptability, it has recently attracted attention as a pollution-free power generation system. The fuel cell power generation system includes a fuel reformer, a fuel cell main body, and respective accessories. The fuel cell body generates a battery reaction by the supplied fuel and air to cause a cell reaction. At this time, the fuel supplied to the fuel cell body is reformed by reforming a hydrocarbon-based raw fuel such as natural gas or an alcohol-based raw fuel such as methanol by a fuel reformer into a hydrogen-rich gas under a reforming catalyst. Gas is used.

In the catalyst layer made of a reforming catalyst in the above-described fuel reformer, when the raw fuel is methane, the reaction represented by the following formulas (1) and (2) is performed by a reforming catalyst typified by Ni system or the like. At a reaction temperature of 600 to 900 ° C. CH ₄ + H ₂ O → CO + 3H ₂ ΔH = −49.3 kcal──── (1) CH ₄ + H ₂ O → CO ₂ + H ₂ ΔH = 9.8 kcal──── (2) The above (1), Formula (2): CH ₄ + 2H ₂ O → CO ₂ + 4H ₂ ΔH = −39.5 kcal──── (3) Fuel reformer for reforming the reforming raw material gas composed of methane as described above The steam reforming reaction in the catalyst layer is an endothermic reaction and requires external heat supply.

Therefore, when the above-mentioned steam reforming reaction is carried out, the reforming raw material gas is passed through a reaction tube containing a catalyst layer, and the reaction tube is heated to supply heat to the catalyst layer.

Conventionally, single-tube, double-tube and cylindrical reactors are known as the above-mentioned reaction tubes. FIG. 5 shows a single tube type reaction tube. The reaction tube 1 is composed of a single tube 2 and a catalyst layer 4 in which a reforming catalyst 3 is filled. The reforming raw material gas flowing through the catalyst layer 4 is reformed into a hydrogen-rich gas.

FIG. 6 shows a double tube type reaction tube.
Is composed of an inner tube 7, a container-shaped outer tube 8 surrounding the inner tube 7, and a catalyst layer 4 in which the reforming catalyst 3 is filled between the inner tube 7 and the outer tube 8. The reaction tube 6 is heated from
The reforming raw material gas is passed through the catalyst layer 4 between the inner tube 8 and the outer tube 8 to reform the gas into a gas rich in hydrogen, and the reformed gas is sent out through the inner tube 7 to the outside.

The above-mentioned single-tube and double-tube reaction tubes 1, 6
When the fuel reformer having the above is started, the reaction tubes 1 and 6 are heated from the outer periphery thereof to a temperature suitable for the steam reforming reaction, and then the reforming raw material gas flows into the reaction tubes 1 and 6. To a gas rich in hydrogen.

In a fuel reformer having such reaction tubes 1 and 6, since the reaction tubes 1 and 6 are heated from the outside, the single tube 2 and the outer tube 8 are thermally expanded, so that the catalyst in the reaction tube is heated. No pressure is applied to the layer 4, so that the reforming catalyst does not collapse. However, in the on-site fuel cell power generator, the thickness of the catalyst layer in the reaction tube is reduced to improve the heat transfer, but the fuel having the cylindrical reaction tube in which the reforming catalyst is easily crushed for the reason described later. A reformer is used.

FIG. 7 is a sectional view of a fuel reformer having a cylindrical reaction tube. In the figure, a furnace vessel 10 is provided with a burner 12 surrounded by a burner tile 11 in the upper center, and an exhaust gas outlet 13 for discharging combustion gas generated by burning fuel from the burner 12 in an upper side wall. Built-in reforming tube 14 having

The reforming pipe 14 includes an inner pipe 15 in which the burner 12 faces the inside, an outer pipe 16 surrounding the inner pipe 15, a bottom plate 17 for closing the lower opening, and the inner pipe 15 and the outer pipe 16. An outer tube 18 is interposed between the inner tube 15 and the outer tube 18, and a catalyst layer 20 filled with a reforming catalyst 19 is built in the annular space between the inner tube 15 and the outer tube 18. Tube 21
Are formed. In addition, a reforming material gas passage 22 through which the reforming material gas flows is formed between the outer tube 18 and the outer tube 16.

The upper openings of the outer pipe 18 and the outer pipe 16 of the reforming pipe 14 communicate with a reforming raw material gas manifold 23 provided at an upper part of the furnace vessel 10.
Reference numeral 3 denotes a reforming material gas inlet 24 into which the reforming material gas flows. The upper openings of the inner pipe 15 and the outer pipe 18 communicate with a reformed gas manifold 25 provided at the upper part of the furnace vessel 10, and the reformed gas manifold 25 has a reformed gas outlet 26 for sending the reformed gas to the outside. It has.

A combustion chamber 27 is formed inside the inner tube 15, and a combustion gas passage 28 is provided between the outer tube 16 and the furnace vessel 10.
Is formed.

With such a configuration, when the fuel from the burner 12 is burned, the combustion gas flows downward through the combustion chamber 27 along the inner surface of the inner pipe 15 as indicated by the arrow, and at the lower end of the reforming pipe 14. After being turned back and flowing through the combustion gas passage 28 along the outer surface of the surrounding tube 16 to heat the reforming tube 24 having the reaction tube 21, the gas is discharged from the exhaust gas outlet 13 to the outside.

On the other hand, the reforming raw material gas flows downward through the reforming raw material gas passage 22 through the reforming raw material gas inlet 23 through the reforming raw material gas inlet 24, and flows into the catalyst layer 20 at the lower end thereof. Then, the reforming raw material gas flows upward from below in the catalyst layer 20 heated by the combustion gas, and is steam-reformed into a hydrogen-rich gas under the catalytic action, passes through the reforming gas manifold 25, and exits from the reforming gas outlet. 26 to the fuel cell.

When the fuel reformer is started from a cold state, the operation is performed as follows. A predetermined amount of fuel from the burner 12 is burned in the combustion chamber 27. The combustion gas generated at this time flows from the combustion chamber 27 to the combustion gas passage 28. The reforming tube 14 is heated by the combustion gas, and the temperature of the reaction tube 21 containing the catalyst layer 20 is set to a temperature suitable for reforming.
Heat to 0 ° C. After the temperature rise, the reforming raw material gas is supplied from the reforming raw material gas inlet 24 through the reforming raw material gas passage 22 to the reaction tube 2.
The reforming is started by flowing through the first catalyst layer 20.

[0016]

As described above, the cylindrical fuel reformer used in the on-site fuel cell power generator differs from the single-tube and double-tube fuel reformers in that the reforming catalyst is crushed. The problem arises. Hereinafter, this problem will be described.

In the above-described fuel reformer of the on-site fuel cell power generator, the reaction tube repeatedly expands and contracts as a result of a heat cycle in which starting and stopping are frequently repeated. At this time, when the fuel reformer is started, the fuel from the burner 12 burns in the combustion chamber 27 formed inside the inner pipe 15, and the combustion gas generated by this combustion flows from the combustion chamber 27 through the combustion gas passage 28 to reform. Since the tube 14 is heated, the temperature of the inner tube 15 becomes higher than that of the outer tube 18 and the outer tube 16. As a result, the gap in the catalyst layer space is reduced since the thermal expansion of the inner tube 15 in the circumferential direction is larger than that of the outer tube 18 at every startup. Due to the decrease in the gap, a compressive force is applied to the catalyst layer 20, and the reforming catalyst is crushed. FIG.
Is a reforming pipe 1 that generates a compressive force that causes such crushing.
4 shows the decrease in the gap due to the temperature difference between the inner pipe 15 and the outer pipe 16, that is, the displacement amount and the rate at which the reforming catalyst is broken.

The amount of displacement between the inner pipe 15 and the outer pipe 16 of the reforming pipe 14 caused during the heat cycle of the start and stop is such that the temperature difference between the inner pipe 15 and the outer pipe 16 reaches 400 ° C. immediately below the burner. In this case, it is about 1 mm. Here, since the temperature of the outer tube 18 is almost the same as the temperature of the outer tube 16, the gap in the catalyst layer space between the inner tube 15 and the outer tube 18 also decreases. In addition, it is understood from FIG. 8 that the reforming catalyst collapses by about 15 (wt%) due to this compressive force.

Note that an AE (Acoustic Emiss
FIG. 9 shows the result of acoustically measuring the cracking of the reforming catalyst that occurs when the fuel reformer is started from the cold with the ion) sensor attached. It is understood from the figure that about 80% of the cracks in the reforming catalyst occurred in the initial 20 minutes of the start-up time of the fuel reformer.

[0020] The pressure crush of the reforming catalyst causes the reforming catalyst to be powdered. As a result, there is a problem that the fluid resistance increases and the fuel reformer cannot be operated.

An object of the present invention is to provide a method of starting a fuel reformer which can reduce the crush of a reforming catalyst filled in a reaction tube when the fuel reformer having a cylindrical reaction tube is started. It is to be.

[0022]

In order to solve the above-mentioned problems, according to the present invention, there is provided an inner tube and an outer tube surrounding the inner tube,
A reaction tube containing a catalyst layer filled with a reforming catalyst between the inner tube and the outer tube; and a burner provided at one end inside the inner tube, and fuel from the burner is supplied to the inner tube. In the fuel reformer that heats the reaction tube with the heat medium burned inside the fuel tank and reforms the hydrocarbon-based raw fuel flowing through the catalyst layer into a hydrogen-rich gas, the amount of combustion by the burner is started from the start of combustion It is assumed that the temperature of the reaction tube is gradually increased as time elapses and the temperature of the reaction tube is raised to a temperature suitable for reforming.

The amount of combustion by the burner is increased stepwise from the start of combustion.

[0024]

[Function] When the fuel reformer is started, it consists of an inner pipe and an outer pipe,
A reaction tube having a catalyst layer filled with a reforming catalyst between the inner tube and the outer tube is heated by a heat medium by burning fuel from a burner provided at one end inside the inner tube. When the temperature rises, the amount of combustion by the burner increases gradually with the elapse of the startup time from the start of combustion.In this method, the temperature difference between the inner tube and the outer tube is reduced by increasing the temperature in a stepwise manner. The thermal expansion difference between the inner and outer tubes in each direction is reduced. As a result, the displacement of the decrease in the gap between the inner tube and the outer tube is reduced, the compressive force applied to the catalyst layer is reduced, and the crushing of the reforming catalyst is reduced.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the relationship between the amount of combustion by a burner and the startup time when the startup of the fuel reformer shown in FIG. 7 is performed by the startup method according to the present invention and the startup method according to the prior art. In FIG. 1, the amount of combustion by the burner 12 at the time of starting according to the starting method of the present invention does not make the amount of combustion constant during the starting time as in the conventional case, but makes the amount of combustion smaller at the start of combustion than the conventional amount of combustion. As the start-up time elapses, the combustion amount increases stepwise as indicated by A, B, C, and D.

FIG. 2 is a temperature rise curve of the inner tube skin temperature of the reaction tube when the temperature of the reaction tube is raised at the time of startup according to the startup method according to the present invention and the prior art. In the figure, when the inner tube skin temperature is raised to 750 ° C., which is a temperature suitable for reforming, the combustion rate is increased stepwise according to the present invention. The starting time to reach a temperature suitable for the reforming is larger in the latter stage, and the starting time according to the present invention is almost the same as the conventional one.

At this time, the temperature of the inner pipe and the outer pipe according to the starting method of the present invention is a temperature rising curve shown in FIG. 3, and the temperature difference ΔT ₁ between the inner pipe 15 and the outer pipe 16 at the initial stage of the startup is About 30
0 ° C. This temperature difference ΔT ₁ is about 500 of the temperature difference ΔT _{2 in} the initial stage of startup based on the temperature rise curve between the inner pipe 15 and the outer pipe 16 when the conventional burner shown in FIG. It is much smaller than ℃.
Therefore, the inner tube 15 and the outer tube 21 in which the catalyst layer 20 is built
The temperature difference with this also becomes smaller than the conventional one,
As a result, the collapse of the reforming catalyst is reduced.

When the starting method according to the present invention is employed as described above, cracks in the reforming catalyst are acoustically investigated by an AE sensor, and as shown in FIG. It is understood that it is considerably less than that.

[0029]

As is clear from the above description, according to the present invention, when the fuel reformer having the cylindrical reaction tube is started,
By gradually increasing the amount of combustion by the burner from the start of combustion, and gradually increasing it in a stepwise manner as a method, the temperature difference between the inner tube and the outer tube of the reaction tube heated by the heat medium due to the combustion of the fuel from the burner is reduced. As a result, the difference in thermal expansion between the inner tube and the outer tube in the circumferential direction becomes smaller, so that the compressive force applied to the catalyst layer in the reaction tube also becomes smaller. It is possible to prevent the increase of the fluid resistance due to the pulverization and prevent the operation from being disabled.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a combustion amount and a starting time when a starting method of a fuel reformer according to an embodiment of the present invention is adopted and when a conventional starting method is used.

FIG. 2 is a heating curve diagram showing a heating state of a reaction tube skin temperature according to the present invention and the conventional starting method of FIG. 1;

FIG. 3 is a heating curve diagram showing a heating state of an inner tube and an outer tube of a reforming tube having a reaction tube when the method of starting the fuel reformer according to the present invention of FIG. 1 is employed.

FIG. 4 is a heating curve diagram showing a heating state of an inner tube and an outer tube of a reforming tube having a reaction tube by a conventional method of starting a fuel reformer.

FIG. 5 is a sectional view of a single tube type reaction tube.

FIG. 6 is a sectional view of a double tube type reaction tube.

FIG. 7 is a cross-sectional view of a fuel reformer having a cylindrical reaction tube.

8 is a diagram showing a temperature difference between an inner tube and an outer tube of a reforming tube having a reaction tube of the fuel reformer of FIG. 7, and a relationship between a displacement amount corresponding thereto and a ratio of a broken catalyst.

FIG. 9 is a diagram showing the relationship between the number of cracks of the catalyst measured by the AE sensor and the start-up time when the start-up method of the fuel reformer according to the related art and the present invention is adopted.

[Explanation of symbols]

 12 Burner 15 Inner tube 16 Outer tube 18 Outer tube 19 Reforming catalyst 20 Catalyst layer

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Motoichi Ikeda 2-6, B9, Kuki, Zushi City, Kanagawa Prefecture (72) Inventor Nobuhiro Iwasa 910-55, Katsuragicho, Kishiwada City, Osaka (72) Inventor Hiromasa Yoshida Aichi Prefecture 1-9-6 Oshikiri, Nishi-ku, Nagoya-shi (72) Inventor Isao Nakagawa 1-1, Tanabe-shinda, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (56) References JP-A-62-106834 (JP, A) JP-A-3-245833 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B01J 8/06 C01B 3/38

Claims (2)

(57) [Claims] 1. A reaction tube having an inner tube and an outer tube surrounding the inner tube, and a reaction tube containing a catalyst layer filled with a reforming catalyst between the inner tube and the outer tube; A burner provided at one end, wherein the fuel from the burner heats the reaction tube with a heat medium burned inside the inner tube to flow the hydrocarbon-based raw fuel flowing through the catalyst layer into a hydrogen-rich gas. In the fuel reformer, the amount of combustion by the burner is gradually increased with the elapse of the start time from the start of combustion to raise the temperature of the reaction tube to a temperature suitable for reforming. How to start the vessel. 2. The starting method of a fuel reformer according to claim 1, wherein the amount of combustion by the burner is increased stepwise from the start of combustion.