JP2012218965A - Hydrogen generator and fuel cell system equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that start and stop of a hydrogen generator break a reforming catalyst, resulting in a reduced lifetime of the hydrogen generator.SOLUTION: The hydrogen generator includes a burner 2 burning a fuel to generate a burning gas, an inner cylinder 14 to be heated by the burning gas of the burner 2, an outer cylinder 15 arranged outside the inner cylinder 14 and a reforming catalyst layer 16 which contains a reforming catalyst 4 reforming a supplied raw gas to generated a reformed gas and is arranged between the inner and outer cylinders. The diameter of the inner cylinder of the reforming catalyst layer 16 is larger in the downstream than in the upstream of the flow of the raw gas.

Description

  The present invention relates to a fuel cell power generation apparatus that generates electricity using a hydrocarbon compound raw material as a raw material, and relates to prevention of destruction of a catalyst used in a hydrogen generation apparatus that supplies hydrogen to the fuel cell.

  A fuel cell power generator includes a fuel cell, a hydrogen generator that supplies fuel gas containing hydrogen to the fuel cell, an inverter circuit that converts DC power generated by the fuel cell into AC power, and a control device that controls them Etc. Various types of fuel cells are used. Currently, polymer electrolyte fuel cells are in widespread use. There are also several types of hydrogen generators. Generally, a reforming catalyst carrying ruthenium or the like is used, and hydrogen is increased by a steam reforming reaction in which a hydrocarbon compound as a raw material is reacted with steam. A reforming unit that generates a reformed gas included in the concentration and a carbon monoxide reducing unit that reduces carbon monoxide contained in the reformed gas.

  In order to generate a sufficient amount of hydrogen by the steam reforming reaction, it is necessary to heat the reaction raw material and the reforming catalyst to a high temperature of 600 ° C. or higher. A typical reforming unit, for example, as disclosed in Patent Document 1, is filled with a granular reforming catalyst in an annular space of a double pipe composed of an inner cylinder and an outer cylinder, and the inner surface of the inner cylinder is heated to a heating source. It becomes the structure heated with the high-temperature combustion gas which becomes.

  Since the fuel cell power generation device is repeatedly started and stopped according to the power load, the hydrogen generator is also repeatedly started and stopped accordingly. Therefore, the reforming catalyst and the inner and outer cylinders are repeatedly heated and cooled from room temperature to 600 ° C. or higher. Due to this heating and cooling, the reforming catalyst is cracked, and there are problems such as deterioration of reforming performance and blockage of the flow path due to the reforming catalyst powder. Therefore, Patent Document 1 proposes a technique for preventing the destruction of the catalyst by providing a plurality of partition plates in the reforming catalyst layer.

  Patent Document 2 proposes a technique for preventing the destruction of the catalyst by disposing an elastic sheet such as foam metal on the surface of the inner cylinder or the outer cylinder that contacts the reforming catalyst.

JP-A-8-208202 JP 2007-210844 A

  However, although the technique of Patent Document 1 can suppress the destruction of the reforming catalyst to some extent, the effect is not sufficient, and the structure is complicated, so that it takes a lot of time to manufacture. was there. On the other hand, the technique of Patent Document 2 has a problem that the elastic sheet loses elasticity while being exposed to a thermal cycle between room temperature and high temperature, and the effect cannot be obtained.

  The present invention solves the above-described conventional problems and provides a catalyst destruction prevention measure that maintains its effect with a simple configuration.

In order to solve the above-described conventional problems, the hydrogen generator of the present invention includes:
A burner that burns fuel and generates combustion gases;
An inner cylinder heated by the combustion gas of the burner;
An outer cylinder disposed outside the inner cylinder;
A reforming catalyst layer that reforms the supplied source gas to generate a reformed gas, and includes a reforming catalyst layer disposed between the inner cylinder and the outer cylinder,
The diameter of the inner cylinder of the reforming catalyst layer is configured to be larger on the downstream side than on the upstream side of the flow of the raw material gas.
The diameter of the inner cylinder between the upstream side and the downstream side of the inner cylinder is configured to be at least equal to or larger than the diameter of the upstream side.

Further, the diameter of the inner cylinder of the portion forming the reforming catalyst layer is configured such that the downstream is always larger than the upstream in the flow of the raw material gas,
The expansion ratio of the diameter of the inner cylinder is configured so that the downstream side is larger than the upstream side in the flow of the raw material gas.

As a result, it is possible to reduce the compression force applied to the reforming catalyst layer in the radial direction from the inner cylinder to the outer cylinder at the start of heating when the hydrogen generator is started, and to prevent the reforming catalyst from being destroyed. .
Furthermore, the diameter of the outer cylinder of the portion forming the reforming catalyst layer is configured to be larger on the downstream side than on the upstream side in the flow of the raw material gas.

  As a result, it is possible to reduce the compressive force applied to the reforming catalyst layer in the radial direction from the outer cylinder to the inner cylinder when the temperature of the reforming unit is lowered when the hydrogen generator is stopped. Can be prevented.

  According to the hydrogen generator of the present invention, it is possible to obtain a hydrogen generator that can greatly reduce the destruction of the reforming catalyst even when the hydrogen generator is repeatedly started and stopped.

Schematic configuration diagram of a hydrogen generator having an evaporation section according to the present invention Principle explanatory diagram of the present invention Principle explanatory diagram of the present invention Schematic configuration diagram of the reforming catalyst layer in Embodiment 1 of the present invention Schematic configuration diagram of the reforming catalyst layer portion in another configuration of the first embodiment of the present invention Schematic configuration diagram of the reforming catalyst layer in Embodiment 2 of the present invention Schematic configuration diagram of the reforming catalyst layer in Embodiment 3 of the present invention Schematic configuration diagram of the reforming catalyst layer portion in another configuration of Embodiment 3 of the present invention

Hereinafter, an embodiment of a hydrogen generator according to the present invention will be described with reference to FIG.
The operation of the hydrogen generator 1 is to first generate a reformed gas containing hydrogen, carbon dioxide, carbon monoxide, and unreacted methane and steam by a steam reforming reaction using a hydrocarbon compound and steam as raw materials. Next, the carbon monoxide reducing unit removes carbon monoxide that is harmful to the fuel cell to generate a fuel gas, and the fuel cell uses this fuel gas to generate power.

  The water vapor necessary for the steam reforming reaction is obtained by evaporating water in the evaporation section located upstream of the reforming section. At this time, as the heat source required for evaporation, the retained heat of combustion gas obtained by burning unused fuel discharged from the fuel cell is usually used.

  An unused fuel gas discharged from the fuel cell 3 is used as the fuel of the burner 2 that supplies reaction heat necessary for the steam reforming reaction located in the center of FIG. In addition, there is a method of supplying fuel separately from not only unused fuel gas. The reforming catalyst 4 may be in the form of particles in which a noble metal such as ruthenium having a catalytic action is supported on porous alumina having a diameter of about 2 to 3 mm, or in the form of a honeycomb in which a noble metal is supported on the surface of a honeycomb material. . The reforming catalyst 4 reacts a mixed gas of a raw material and steam with hydrogen, carbon dioxide, carbon monoxide, and a reformed gas containing unreacted methane and steam by a steam reforming reaction. Carbon monoxide reacts with the water vapor in the reformed gas by the shift catalyst 5 to reduce its concentration to about 1% or less. The reformed gas is further mixed with air supplied from the air supply port 6, and carbon monoxide is selectively burned and removed by the selective oxidation catalyst 7. The generated fuel gas is sent from the fuel gas outlet 8 to the fuel cell 3. The heat insulating material 9 is disposed outside the hydrogen generating device to insulate the entire hydrogen generating device, and the combustion gas exhaust port 10 of the burner 2 and the hydrocarbon and water supply ports 11 as raw materials are formed. The supplied water evaporates when it flows down in the evaporation section 13 formed in a spiral shape by the spiral rod 12. The reforming catalyst 4 is disposed in an annular space formed by the inner cylinder 14 and the outer cylinder 15 to form a reforming catalyst layer 16. Reference numeral 17 denotes a fuel gas passage cylinder that forms a fuel gas passage.

  The present invention relates to the shapes of the inner cylinder 14 and the outer cylinder 15 that form the reforming catalyst layer.

(Embodiment 1)
Hereinafter, the hydrogen generator according to Embodiment 1 of the present invention will be described in detail with reference to FIGS.

  2A and 2B are explanatory diagrams of the principle of the present invention. First, the cause of the destruction of the reforming catalyst in the conventional hydrogen generator will be described with reference to FIG.

  FIG. 2A is an enlarged view of a part of the reforming catalyst layer 16 having the reforming catalyst 4 while using a conventional cylindrical inner cylinder and outer cylinder. In FIG. 2-A having a conventional cylindrical shape, the inner cylinder 14 and the outer cylinder 15 are simple cylindrical cylinders. When the hydrogen generator is activated, the burner 2 in FIG. 1 is ignited and the reforming catalyst layer 16 begins to be heated. The state of the reforming catalyst layer 16 at that time is illustrated in FIG. In the initial stage of startup, the inner cylinder 14 is thermally deformed by the high-temperature combustion gas of the burner 2, but the outer cylinder 15 is hardly thermally deformed because heat has not yet reached. In the hydrogen generator of FIG. 1, the entire reforming catalyst layer 16 extends downward due to thermal expansion. At the initial stage when the reforming catalyst layer 16 starts to be heated, for example, the position of an arbitrary region a of the inner cylinder 14 moves from the A position to the B position as indicated by the arrow Y1 in the drawing due to the longitudinal extension. At the same time, since the diameter of the cylinder expands when heated, it moves from the B position to the C position as shown by the arrow Y2. Meanwhile, the outer cylinder 15 is hardly thermally deformed because heat has not reached. Therefore, the width of the annular space filled with the reforming catalyst 4 is reduced from L1 to L2 in the drawing. As a result, the particles of the reforming catalyst 4 are compressed and destroyed.

Therefore, in the present invention, as shown in FIG. 2B, the diameter of the inner cylinder 14 is increased toward the downstream in the raw material flow direction. At the initial stage of starting the hydrogen generator, the position of an arbitrary region a of the inner cylinder extends as indicated by an arrow Y1 in the vertical direction and moves from the first A position to the B position. At the same time, the diameter expands and moves from the B position to the C position as shown by the arrow Y2. That is, the region a moves from the A position to the C position, and since this position is a position where the inner cylinder 14 exists before the start, the particles of the reforming catalyst 4 are not subjected to a compressive force. The reforming catalyst 4 is not destroyed. The region a of the inner cylinder 14 moves only in the direction of the arrow Y3 by heating and cooling, and does not apply a compressive force to the reforming catalyst 4. Thus, destruction of the catalyst at the time of starting the hydrogen generator can be prevented by increasing the diameter of the inner cylinder 14 in which the catalyst is disposed in the raw material flow direction. Note that the catalyst is not limited to the particulate form, but the honeycomb form can also be prevented from being broken.

  On the other hand, the thermal contraction of the reforming catalyst layer 16 will be described with reference to FIGS. FIG. 3A illustrates the state of the reforming catalyst layer 16 in a stopped state when the outer cylinder 15 is a simple cylindrical shape. As described above, the arbitrary region a of the inner cylinder 14 only moves in the direction of the arrow Y3 by heating and cooling, and does not compress and destroy the reforming catalyst 4. However, the arbitrary region b of the outer cylinder 15 contracts in the direction of the arrow Y1 due to cooling after operation stop, moves from the A position to the B position, and further contracts in the direction of the arrow Y2 to reduce the diameter. Move to position. By this contraction, the reforming catalyst 4 is compressed and destroyed.

  On the other hand, in FIG. 3B of the present invention, the outer cylinder 15 is configured to have a larger diameter in the raw material flow direction, like the inner cylinder 14. The movement of the arbitrary region b of the outer cylinder 15 in FIG. 3B when the operation is stopped is contracted in the direction of the arrow Y1 by cooling and moved from the A position to the B position, and the diameter is also changed to the arrow Y2. Although it contracts in the direction and moves to the C position, this position is a position where the outer cylinder 15 was present before the operation was stopped, and no force to be compressed by the reforming catalyst 4 is applied. Compressive fracture of the reforming catalyst 4 can be prevented.

  FIG. 4 shows a specific configuration of the present invention. FIG. 4 shows the reformed portion of the hydrogen generator 1 shown in FIG. In FIG. 4, the same reference numerals are given to the same components as those in FIG. In the embodiment of FIG. 4, the diameters of the inner cylinder 14 and the outer cylinder 15 are configured so as to be curved as a whole from the A portion of the reforming catalyst layer inlet to the B portion of the reforming catalyst layer outlet. ing. With this configuration, as described above, it is possible to prevent the reforming catalyst 4 from being destroyed when the hydrogen generator is started and stopped. In the figure, reference numeral 19 denotes an elastic portion provided in the bottom plate 19 to absorb deformation due to thermal expansion and contraction of the inner cylinder 14 and expansion and contraction, and increase / decrease in diameter, and the cylinder 20 constitutes the outermost generated gas flow path. To do.

  In addition, the example comprised so that the said deformation | transformation of the inner cylinder 14 may not be prevented is shown in FIG. In FIG. 5, the inner cylinder 14 and the cylinder 20 are connected, and a heat insulating block 21 is disposed immediately below the fuel gas flow path cylinder 17. By configuring in this way, deformation is facilitated without hindering the increase or decrease of the diameter due to the expansion and contraction of the downstream end of the inner cylinder 14.

(Embodiment 2)
Hereinafter, a fuel cell power generator according to Embodiment 2 of the present invention will be described with reference to FIG. In FIG. 6, the same numbers are assigned to the same components as those in the above-described embodiment.
Compared with the embodiment shown in FIG. 4, in the embodiment of FIG. 6, the diameters of the inner cylinder 14 and the outer cylinder 15 are linearly increased in the flow direction of the raw material. By constituting in this way, the structure of the reforming part can be simplified, and the production can be made easier.

(Embodiment 3)
Hereinafter, a fuel cell power generator according to Embodiment 3 of the present invention will be described with reference to FIG. Also in FIG. 7, the same number is given to the same component as the above-mentioned embodiment. In this embodiment, the diameters of the inner cylinder 14 and the outer cylinder 15 are the same from the A part of the reforming catalyst layer inlet to the C part in the middle, and gradually increased from C part to B part of the reforming catalyst layer outlet. Yes. Since the upstream portion of the reforming catalyst layer 16 has a relatively low temperature of about 300 to 400 ° C., the reforming catalyst 4 is hardly destroyed at this portion. Therefore, the diameters of the inner cylinder 14 and the outer cylinder 15 are configured to increase in the raw material flow direction only in the high temperature portion where the reforming catalyst 4 is destroyed. By configuring in this way, the rate of change in the size of the diameter in the flow direction from part C to part B is designed to be larger as required within the range of the defined hydrogen generation layer and the overall diameter. Therefore, destruction of the reforming catalyst 4 can be prevented more effectively.

  6 and the embodiment of FIG. 6 are combined, and the diameters of the inner cylinder 14 and the outer cylinder 15 downstream from the C portion in the middle of the reforming catalyst layer are linearly increased as shown in FIG. As a result, the structure of the reforming part can be simplified, and the production can be facilitated.

  Moreover, the hydrogen generator of Embodiments 1-3 can be used for the hydrogen generator of a fuel cell system.

  Since the fuel cell hydrogen generator of the present invention can greatly reduce the destruction of the reforming catalyst, the hydrogen generator can be used for a long period of time.

DESCRIPTION OF SYMBOLS 1 Hydrogen generator 2 Burner 3 Fuel cell 4 Reforming catalyst 5 Shifting catalyst 7 Selective oxidation catalyst 9 Heat insulating material 10 Exhaust port 11 Supply port 14 Inner cylinder 15 Outer cylinder 16 Reformed catalyst layer 20 Cylinder

Claims (5)

A burner that burns fuel and generates combustion gases;
An inner cylinder heated by the combustion gas of the burner;
An outer cylinder disposed outside the inner cylinder;
A reforming catalyst layer having a reforming catalyst for reforming the supplied raw material gas to generate a reformed gas, and disposed between the inner cylinder and the outer cylinder;
With
The hydrogen generator configured such that the diameter of the inner cylinder of the reforming catalyst layer is larger on the downstream side than on the upstream side of the flow of the raw material gas.   2. The hydrogen generator according to claim 1, wherein a diameter of the inner cylinder between an upstream side and a downstream side of the inner cylinder is configured to be at least equal to or larger than a diameter of the upstream side. The diameter of the inner cylinder of the portion forming the reforming catalyst layer is configured such that the downstream is always larger than the upstream in the flow of the raw material gas,
3. The hydrogen generator according to claim 1, wherein the ratio of the diameter expansion of the inner cylinder is configured such that the downstream side is larger than the upstream side in the flow of the raw material gas.   The diameter of the said outer cylinder of the part which forms the said reforming catalyst layer is comprised so that the downstream may become larger compared with the upstream in the flow of raw material gas. 2. The hydrogen generator according to claim 1.   The fuel cell system provided with the hydrogen generator described in any one of Claims 1-4.

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