JP2703831B2 - 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 fuel cell in which a hydrocarbon-based raw fuel is passed through a reforming pipe, and the raw fuel is steam-reformed with a reforming catalyst to reform a hydrogen-rich reformed gas. The present invention relates to a fuel reformer for a power generator.

[0002]

2. Description of the Related Art Hydrogen-rich reformed gas is generated from a hydrocarbon-based raw fuel such as natural gas or naphtha by adding steam and heating with a heat medium while using a reforming catalyst to generate hydrogen-rich reformed gas. A fuel reformer shown in FIG. 3 has been already proposed by the same applicant as Japanese Patent Application No. 2-40038 as a fuel reformer supplied to a fuel cell via a carbon oxide converter. In FIG.
Is a reforming tube of which at least a lower part is covered by a furnace container 3, and a burner 2 is disposed inside the reforming tube. The reforming tube 1 includes an upright partition cylinder 4, and an inner cylinder 5 and an outer cylinder which are concentrically arranged inside and outside of the partition cylinder 4 with a lower portion separated from a lower end of the partition cylinder 4 and connected by a ring-shaped bottom plate 7. 6 are formed. With such a configuration, a double annular space of the inner annular space 8 and the outer annular space 9 communicating with the lower end portion is formed in the reforming tube 1. A source gas inlet 11 is formed above the outer annular space 9 via a source gas manifold 10, and a reformed gas outlet 13 is formed above the inner annular space 8 via a reformed gas manifold 12. . The reforming pipe 1 is filled with a granular reforming catalyst 14 in the entire inner annular space 8 except for the reformed gas manifold 12. Burner 2
Is disposed inside the reforming tube 1. A refractory heat insulating material 15 is disposed below and around the reforming tube 1 at a distance from the reforming tube, and a heat medium passage 16 for guiding a heat medium from the burner 2 is formed between the heat insulating material 15 and the reforming tube 1. I have. This heat medium passage 16
A heat medium outlet 18 is formed at an upper portion of the device through a heat medium outlet manifold 17.

[0003] In the fuel reformer configured as described above,
Fuel (fuel gas exhausted from the fuel cell main body during fuel cell operation) is introduced into the burner 2 from a fuel inlet 19 and burns with combustion air from an air inlet 20 to generate a heat medium as combustion gas. The heat medium flows downward along the inside of the reforming tube 1 along the reforming catalyst filling portion, and subsequently flows through the heat medium passage 1.
6, and is discharged from the heat medium outlet 18 through the heat medium manifold 17. On the other hand, the raw material gas composed of raw fuel and water vapor flows in from the raw material gas inlet 11, flows downward through the outer annular space 9 through the raw material gas manifold 10, returns to the lower end of the partitioning cylinder 4, and enters the inner annular space 8. The gas flows upward in the reforming catalyst layer filled in the inner annular space 8 and is reformed into a reformed gas rich in hydrogen.
2 through the reformed gas outlet 13. The heat transfer to the raw material gas flowing through the outer annular space 9 is improved by narrowing the gap of the heat medium passage 16 to increase the flow rate of the heat medium, and accordingly, the temperature of the heat medium exhaust gas is reduced. Can be.

In the above-described fuel reformer, when a raw fuel such as natural gas is subjected to steam reforming, a reforming reaction is carried out at a high operating temperature, and the heat-resistant The surface temperature of steel is 700-900 ° C, depending on operating conditions.
Also. Further, the above-mentioned fuel reformer uses the reformed gas obtained by converting the hydrogen-rich reformed gas obtained in the fuel reformer into a gas having a low carbon monoxide concentration in a carbon monoxide converter as fuel for a fuel cell. It is incorporated in a fuel cell power generator that supplies power and generates power using a fuel cell. It is incorporated in such a fuel cell power generator. It is desired that the start and stop time of the entire fuel cell power generation device be shorter because of the necessity of being a power generation device, and the target is to be about 1 to 2 hours. If the frequency is the highest, start and stop may be repeated every day. These have a startup time of about 10 to 100 times and a startup and shutdown frequency of about 250 times that of a fuel reformer used for a chemical plant, and start and stop under extremely severe conditions. Is performed.

[0005]

The above-described fuel reformer for a fuel cell power generator according to the prior art is frequently started and stopped under extremely severe temperature change conditions as compared with a reformer for a chemical plant. Are repeated, and the metal plate constituting the reforming tube repeats expansion and contraction. In particular, the temperature rise curves at the time of startup of the portion A of the reforming tube close to the burner 2 and the portion B close to the inlet of the raw material gas shown in FIG. While the temperature rises rapidly with the ignition of the burner, the surface temperature Q of the reforming tube at the inlet of the raw material gas increases immediately after the burner ignition because the amount of heat of the heat medium is consumed for heating the reforming tube and the like. Lately, this results in a temperature distribution with a large temperature difference in the reforming tube immediately after the burner ignition. Due to the temperature distribution of the large temperature difference, the inner cylinder of the reforming tube expands more rapidly than the outer cylinder and the partition cylinder, and the reforming catalyst layer is once subjected to a pressing force in the radial direction. The granular reforming catalyst that has received this pressing force is blocked by the partition cylinder and cannot move in the radial direction, and thus tries to move in the axial direction that matches the direction in which the raw material gas moves. As a result, the granular reforming catalyst moves in the axial direction. Will be subjected to pressure. In the worst case, such a pressing force causes the granular reforming catalyst to be crushed. When the granular reforming catalyst is crushed and becomes powdery, the pressure loss to the fluid in the reforming catalyst layer increases, and in the worst case, the fuel cell power generation This makes it impossible to continue the operation of the device.

As a countermeasure to avoid this, it is necessary to provide the granular reforming catalyst with a required crushing strength. In order to increase the crushing strength of the catalyst itself, it is necessary to increase the strength of alumina as a carrier of the catalyst. Required. For this purpose, the γ-alumina is converted into α-alumina to increase the crystallinity by either raising the firing temperature during the production of the carrier or lengthening the firing time. However, as a result of increasing the crystallinity, the pore volume inside the carrier is reduced. By the way, the pores inside the carrier directly contribute to the catalytic reaction rate, and the larger the pore volume, the higher the catalytic reaction rate and the higher the catalytic activity. Had become.

[0007] As described above, the relationship between the crushing strength and the activity of the catalyst is in a contradictory relationship. Therefore, the reforming catalyst of the fuel reformer for a fuel cell power generator appropriately balances the crushing strength and the catalytic activity. As a result, the reforming catalyst volume cannot be reduced, and for example, in the case of an on-site fuel cell power generator, the size of the fuel reformer cannot be reduced to a certain extent or less. There was a problem.

An object of the present invention is to provide a reforming catalyst layer in a reforming tube in which a particulate reforming catalyst is used for starting and stopping a fuel reformer,
An object of the present invention is to provide a fuel reformer that does not collapse at the time of temperature decrease.

[0009]

According to the present invention, the object is

1) a reforming tube having a double cylindrical structure filled with a reforming catalyst, a burner installed inside the reforming tube and supplying a heat medium for heating the reforming tube; A furnace vessel configured to form a path of a heat medium and surround at least a lower portion of the reforming pipe. The hydrocarbon-based raw fuel flows through the reforming pipe, and the raw fuel is steamed by the reforming catalyst. In a fuel reformer for reforming into a reformed gas rich in hydrogen, a reforming catalyst layer in the reforming tube is provided with a flexible material for absorbing stress generated in the reforming catalyst due to thermal deformation of the reforming tube. A layer of a neutral stress absorber on a surface perpendicular to the flow direction of the raw material gas, and

2) The means according to the above item 1, wherein the number of layers of the stress absorber is one or more.

3) A reformer having a double cylindrical structure filled with a reforming catalyst, a burner installed inside the reformer and supplying a heat medium for heating the reforming tube, A furnace vessel configured to form a path of a heat medium and surround at least a lower portion of the reforming pipe. The hydrocarbon-based raw fuel flows through the reforming pipe, and the raw fuel is steamed by the reforming catalyst. In a fuel reformer for reforming into a reformed gas rich in hydrogen, a reforming catalyst layer in the reforming tube has a flexibility of absorbing stress generated in the reforming catalyst due to thermal deformation of the reforming tube. Of the small particle-shaped stress absorber together with the particulate reforming catalyst constituting the reforming catalyst layer,

[0013] 4) In the means described in the above items 1 to 3, this is achieved by the fact that the stress absorber is a braided thin metal wire.

[0014]

In the present invention, since the above-described structure is employed, heat is applied to the reforming tube by a temperature distribution having a large temperature difference generated when the fuel reformer having the reforming catalyst layer composed of the granular reforming catalyst is started and stopped. Deformation occurs, and compressive stress is applied to the reforming catalyst layer due to this. At this time, a flexible stress is provided on the reforming catalyst layer at right angles to the axial direction in the direction coinciding with the flow direction of the raw material gas. The flexible flake-shaped stress absorber mixed with the particulate reforming catalyst in the absorber layer or the reforming catalyst layer shrinks its apparent volume according to the applied stress, and is added to the reforming catalyst Reduce compressive stress. The fuel reformer goes into steady operation,
When the temperature difference generated in the reforming tube is reduced and the compressive stress applied to the reforming catalyst layer is reduced, the apparent volume of the stress absorber substantially returns to the original, and the reforming catalyst layer is also substantially restored to the original volume. Return to shape.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a fuel reformer according to one embodiment of the present invention. In FIG. 1, the same components as those in the conventional example of FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted. 1 is different from the conventional example in that a layer of a stress absorber 21 made of a braided flexible thin metal wire such as stainless steel is formed on the reforming catalyst layer of the reforming tube 1 by flowing a raw material gas. That is, one or more layers are provided on a plane perpendicular to the axial direction in the direction corresponding to the direction.

[0016] With such a configuration, a thermal distribution is generated in the reforming tube due to a large temperature difference generated during the start and stop operations of the fuel reformer, which causes a compressive stress applied to the reforming catalyst layer. Is reduced. FIG. 5 shows the results of an experiment on the compressive stress applied to the reforming catalyst layer in the axial direction with respect to the reduction in the thickness of the reforming tube when the thickness of the reforming catalyst layer is 25 mm in the radial direction. Compared to the compressive stress R without the stress absorber according to the configuration of the prior art, the compressive stress S with the stress absorber according to the present invention (5% in the ratio volume of the stress absorber).
Is greatly reduced to about 1/5.

The stress absorber 21 has a width substantially equal to the dimension of the reforming catalyst layer in the thickness direction, and is formed in a ring shape having an inner diameter substantially equal to the inner diameter of the reforming catalyst layer. However, it is assumed that the fuel reformation is such that a rectangular parallelepiped having dimensions substantially equal to or slightly smaller than the thickness direction of the reforming catalyst layer is arranged along the ring-shaped reforming catalyst layer. This is preferable for the work of assembling the porcelain.

FIG. 2 is a sectional view of a fuel reformer according to another embodiment of the present invention. 2, the same components as those of the embodiment of the present invention shown in FIG. 1 and the conventional example shown in FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted. 2 is different from the embodiment of the present invention shown in FIG.
Is contained in the reforming catalyst layer while being mixed with the granular reforming catalyst 14.

With such a configuration, in addition to the advantage of providing the stress absorber 21 in the reforming catalyst layer, a flexible flake-shaped stress absorber 22 is previously provided on the granular reforming catalyst 14. What was mixed at a predetermined volume ratio,
The charging of the reforming catalyst and the stress absorber can be performed at the same time and by a simple operation by charging the fuel into the reforming tube 1, which brings about a favorable advantage in the assembly operation of the fuel reformer.

[0020]

According to the present invention, there is provided a flexible catalyst provided in a reforming catalyst layer made of a reforming catalyst in a reforming pipe on a surface perpendicular to an axial direction in a direction coinciding with a flow direction of a raw material gas. Temperature distribution of large temperature difference generated in the reforming pipe at the time of starting and stopping operation of the fuel reformer due to the layer of flexible stress absorber or the flexible flake-shaped stress absorber mixed in the granular reforming catalyst By absorbing the stress generated in the reforming catalyst layer due to the thermal deformation due to, the compressive stress applied to the reforming catalyst can be significantly reduced. For this reason, it is possible to use a catalyst having a large perforated volume and therefore a low crushing strength but a high reaction rate as a granular reforming catalyst, and the volume of the reforming catalyst layer can be reduced, thereby making the fuel reformer compact. The effect that it can be made is produced.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of a fuel reformer according to another embodiment of the present invention.

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

FIG. 4 is a diagram showing a temperature rise characteristic of a reforming tube when a fuel reformer is started.

FIG. 5 is a diagram showing a relationship between a reduction in the thickness of a reforming tube of a fuel reformer and a compressive stress.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reforming pipe 2 Burner 3 Furnace container 14 Granular reforming catalyst 21 Stress absorber 22 Small stress absorber

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hiromasa Yoshida 1-9-6 Oshikiri, Nishi-ku, Nagoya-shi, Aichi Prefecture (72) Inventor Koichi Kaneko 1-1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. (56) References JP-A-63-201001 (JP, A) JP-A-61-114730 (JP, A) JP-A-4-50101 (JP, A)

Claims (4)

(57) [Claims] 1. A reforming tube having a double cylindrical structure filled with a reforming catalyst, a burner installed inside the reforming tube and supplying a heat medium for heating the reforming tube. A furnace vessel configured to form a path of a heat medium and surround at least a lower portion of the reforming pipe. The hydrocarbon-based raw fuel flows through the reforming pipe, and the raw fuel is steamed by the reforming catalyst. In a fuel reformer for reforming into a reformed gas rich in hydrogen, a reforming catalyst layer in the reforming tube is provided with a flexible material for absorbing stress generated in the reforming catalyst due to thermal deformation of the reforming tube. A fuel reformer, characterized in that a layer of an elastic stress absorber is provided on a plane perpendicular to the flow direction of the raw material gas. 2. The fuel reformer according to claim 1, wherein the number of layers of the stress absorber is one or more. 3. A reforming tube having a double cylindrical structure filled with a reforming catalyst, a burner installed inside the reforming tube and supplying a heat medium for heating the reforming tube, A furnace vessel configured to form a path of a heat medium and surround at least a lower portion of the reforming pipe. The hydrocarbon-based raw fuel flows through the reforming pipe, and the raw fuel is steamed by the reforming catalyst. In a fuel reformer for reforming into a reformed gas rich in hydrogen, a reforming catalyst layer in the reforming tube has a flexibility of absorbing stress generated in the reforming catalyst due to thermal deformation of the reforming tube. A fuel reformer characterized in that the small-piece-shaped stress absorber is mixed and stored together with the granular reforming catalyst constituting the reforming catalyst layer. 4. The fuel reformer according to claim 1, wherein the stress absorber is a thin metal wire braid.