JPH11273703A - High-pressure fuel cell power generation equipment - Google Patents

Abstract

(57) [Problem] To achieve high reforming efficiency as a whole of a power generation facility under high pressure of 10ata or more without increasing the operating temperature of a plate reformer, thereby maintaining high power generation efficiency. Provide high-pressure fuel cell power generation equipment. SOLUTION: In a fuel cell power generation facility for supplying a reformed gas reformed by a reformer 12 to an anode side A of a fuel cell 14, a part of anode exhaust gas discharged from the fuel cell is supplied to an anode side inlet of the fuel cell. An anode gas recycle line 16 for recirculation and a heat insulating reformer 18 installed in the line and holding a reforming catalyst therein are provided. In the adiabatic reformer, the reforming reaction is caused by the sensible heat of the high-temperature anode exhaust gas itself, and the reforming efficiency is increased as a whole of the power generation equipment. In addition, since the generated hydrogen is directly supplied to the anode-side inlet of the fuel cell, the amount of hydrogen in the fuel cell increases, and the power generation efficiency increases.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure fuel cell power generation system capable of suppressing a decrease in a reforming rate due to a high pressure and maintaining a high power generation efficiency.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have features not found in conventional power generation equipment, such as high efficiency and little impact on the environment, and are attracting attention as power generation systems following hydro, thermal and nuclear power. Are being researched and developed in various countries around the world. In particular, in a power generation facility using a molten carbonate fuel cell using natural gas as a fuel, a reformer is used to reform a source gas such as natural gas schematically shown in FIG. 3 into a gas containing hydrogen. . The reformer includes a combustion chamber Co and a reforming chamber Re separated by a partition wall.
(For example, anode exhaust gas from a fuel cell),
The reforming chamber Re is heated by the heat, and the raw material gas 2 flowing through the reforming chamber is reformed into a gas 4 containing hydrogen (hereinafter, referred to as a reformed gas) by the reforming catalyst 3 filled therein. Has become.

[0003] As such a reformer, a tubular type developed for a conventional plant has been developed as disclosed in
No. 35778, JP-B-5-9362, JP-A-62-2
No. 7303 has already been proposed for use in fuel cells.

On the other hand, a plate reformer having a configuration completely different from the above-mentioned conventional tubular reformer has already been proposed by the applicant of the present invention and is partially used. As illustrated in the principle diagram of FIG. 4, the plate reformer is configured such that a reforming chamber Re and a combustion chamber Co are each configured in a plate shape and are alternately stacked, and the combustion chamber Co includes particles. The combustion catalyst 5 is filled in a flat plate shape, and the fuel gas 1 and the combustion air 7 supplied from the external manifolds 6a and 6b flow as indicated by broken lines in FIG. ) And heat is generated, and the flue gas 8 is discharged to the external manifold 6 on the opposite side.
discharged from c. On the other hand, the reforming chamber Re is similarly filled with a particulate reforming catalyst 3 in a plate shape, and the raw material gas 2 supplied from the external manifold 6d flows as shown by a solid line in the drawing, and The raw material gas 2 is reformed by the action of
The reformed gas 4 is discharged from the external manifold 6e on the opposite side.

Further, the fuel chamber Co shown in FIG. 4 is replaced with a heating chamber H through which a high-temperature gas flows, and a separate combustion chamber (for example, a catalytic combustor) for supplying high-temperature combustion exhaust gas to the heating chamber H from another combustor. Other plate reformers have also been developed.
Compared with the tubular reformer, such a plate reformer has a large heat transfer area per volume and has a feature that it can be made very small and lightweight, and is not only used for fuel cells but also used in other fields (for example, hydrogen). Application).

[0006]

In the plate reformer described above, increasing the operating pressure is effective for improving plant efficiency and reducing the size. For this reason, the operating pressure of the plate reformer is adjusted to 10 ata in accordance with the operating pressure of the fuel cell.
It is desired to increase to the above. However, the reforming reaction of methane is CH ₄ + H ₂ O → 3H ₂ + CO. . Since the reaction is represented by the main reaction formula (Formula) and the number of moles (volume) increases by the reaction, the equilibrium constant decreases due to the increase in the pressure, and thus the reforming rate decreases. For example, at a pressure of 10 ata or more, the reforming rate becomes 80% or less, and the required reforming rate of 90% or more cannot be satisfied.

On the other hand, it is possible in principle to improve the reforming rate by increasing the reforming temperature. However, in a plate reformer, the upper limit of the reforming temperature is around 800 ° C. due to the temperature limitation of the partition walls. However, in order to raise the temperature further than this, it is necessary to use a heat-resistant material (for example, a ceramic material) that is very expensive and has poor workability, which is not practical.

[0008] In other words, the reforming rate in the reformer is
Determined by the S / C ratio (steam / carbon ratio), temperature and pressure, the higher the S / C ratio (preferably 3 or more) and the higher the temperature and the lower the pressure, the higher the reforming rate. Therefore, in a high-pressure system with a high operating pressure, even if the S / C ratio and the reforming temperature are the same, the reforming rate is reduced, and the power generation efficiency is reduced. In order to avoid this, increasing the S / C ratio (supplying extra steam) causes a decrease in power generation efficiency,
On the other hand, when using a plate reformer, it is difficult to raise the reforming temperature due to restrictions on materials and the like.

The present invention has been made in order to solve such a problem. That is, an object of the present invention is to obtain a high reforming efficiency as a whole power generation facility under a high pressure of 10 ata or more without increasing the operating temperature of the plate reformer, and thereby maintain a high power generation efficiency. It is to provide a fuel cell power generation facility.

[0010]

According to the present invention, in a fuel cell power generation facility for supplying a reformed gas reformed by a reformer to an anode side of a fuel cell, a part of an anode exhaust gas discharged from the fuel cell is provided. A high-pressure fuel cell power generation facility, comprising: an anode gas recycling line that recirculates fuel gas to an anode-side inlet of a fuel cell; and an adiabatic reformer installed in the line and holding a reforming catalyst therein. .

The hydrogen is consumed by the anode reaction in the fuel cell, and the same amount of water vapor is generated. For this reason, in the gas composition in the anode exhaust gas, the ratio of water vapor to CH ₄ is very large (for example, 10 or more) and high temperature (for example,
(Approximately 00 ° C.), which is a state suitable for reforming with little risk of carbon precipitation. The present invention is based on such a new finding.

That is, an anode gas recycle line for recirculating a part of the anode exhaust gas discharged from the fuel cell to the anode side inlet of the fuel cell is provided, and an adiabatic reformer having a reforming catalyst therein is installed in the line. Thereby, in the heat insulation reformer, the reforming reaction can be promoted by the sensible heat of the high-temperature anode exhaust gas itself. Therefore, under high pressure (for example, 10 ata or more), high reforming efficiency can be obtained as a whole of the power generation equipment. Further, the hydrogen generated by the reforming is directly recycled through the anode gas recycling line to the anode side inlet of the fuel cell, so that the amount of hydrogen supplied to the fuel cell is increased, thereby increasing the power generation efficiency at high pressure. Can be enhanced.

According to a preferred embodiment of the present invention, a recycle blower for pressurizing and sending the anode exhaust gas to the anode gas recycle line is provided. With this configuration,
The reforming rate and the power generation efficiency of the entire power generation facility can be controlled by adjusting the amount of anode exhaust gas flowing through the recycling line.

The reformer is preferably a plate reformer in which a flat reforming chamber Re and a heating chamber H are alternately stacked. With this configuration, the power generation facility can be made compact while maintaining a high reforming rate and power generation efficiency.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common parts are denoted by the same reference numerals. FIG. 1 is a configuration diagram of a high-pressure fuel cell power generation facility according to the present invention. In FIG. 1, a high-pressure fuel cell power generation system 10 of the present invention includes a reformer 12 and a fuel cell 14, and supplies the reformed gas 4 reformed by the reformer 12 to the anode A of the fuel cell 14. It has become. Also, this equipment is, for example, 10ata
The operation is performed under the above high pressure.

In this embodiment, the reformer 12 is a plate reformer in which flat reforming chambers Re and heating chambers H are alternately stacked. As illustrated in the figure, in the reformer 12, a heating chamber H is filled with a combustion catalyst,
The fuel gas 1 (for example, anode exhaust gas) is burned (catalytic combustion) inside. Further, the reforming material Re is filled with a reforming catalyst, and reforms a mixed gas of the raw material gas 2 and the steam 9 to convert it into a hydrogen-rich gas. By using such a plate reformer, the power generation equipment can be made compact.

The present invention is not limited to this configuration, and a configuration may be adopted in which the combustor is provided outside the plate reformer and the combustion exhaust gas is supplied to the heating chamber H. Further, a conventional reformer other than the plate reformer may be used.

In this embodiment, the fuel cell 14 is
This is a molten carbonate type fuel cell using carbonate as an electrolyte and operating at a high temperature of about 650 ° C. The present invention is not limited to this, and may be applied to other types of fuel cells that operate at high temperatures. The anode reaction of a molten carbonate fuel cell is
H ₂ + CO ₃ ^2- → H ₂ O + CO ₂ + 2e ⁻ . . (formula)
The reaction consumes hydrogen and produces the same amount of water vapor. Since the fuel utilization rate in the fuel cell is as high as, for example, about 75 to 80%, hydrogen is significantly reduced as compared with the inlet side, and a large amount of water vapor is generated. For this reason,
The gas composition in the anode exhaust gas is such that the ratio of water vapor to CH ₄ is very large (for example, 10 or more) and the temperature of the anode exhaust gas is high (for example, around 700 ° C.). State.

As illustrated in the figure, a high-temperature gas (cathode gas) containing oxygen that has exited from the heating chamber H of the reformer 12 is supplied to the cathode side C of the fuel cell, and a cathode reaction is internally performed. The high temperature cathode exhaust gas is supplied to, for example, a gas turbine to recover energy.

As shown in FIG. 1, the high-pressure fuel cell power generation system 10 of the present invention includes an anode gas recycling line 16 for recirculating a part of the anode exhaust gas discharged from the fuel cell 14 to the anode side inlet of the fuel cell 14. , A recycle blower 17 and a heat insulating reformer 18 installed in the line.

The adiabatic reformer 18 has a reforming catalyst 3 inside.
It is a chamber in which the outside is kept warm, and the anode exhaust gas in a state suitable for reforming with little risk of carbon deposition directly contacts the reforming catalyst as described above, and the sensible heat of the high-temperature anode exhaust gas itself A reforming reaction is caused. The hydrogen generated by the reforming reaction (formula) is directly recycled to the anode side inlet of the fuel cell via the anode gas recycling line 16 and supplied to the fuel cell.

As shown in FIG. 1, the recycle blower 17 is preferably installed on the downstream side of the heat insulating reformer 18, that is, on the inlet side of the fuel cell. As described above, since the reforming reaction is caused by the sensible heat of the anode exhaust gas itself, the temperature of the anode exhaust gas is lowered by this reforming reaction (for example, about 40 to 50 ° C.), and the cooling of the recycle blower 17 is facilitated, and the reliability is improved. Can be increased. Also,
The amount of the anode exhaust gas flowing through the recycling line can be adjusted by the recycling blower 17 to control the reforming rate and the power generation efficiency of the entire power generation equipment.

[0023]

EXAMPLES Table 1 shows the simulation results of the performance of the present invention described above. In this table, (A) shows the reforming by the plate reformer, (B) shows the condition example of the adiabatic reformer, and (C) shows the overall reforming rate.

[0024]

[Table 1]

From (A) in Table 1, it can be seen that the reforming rate is low under high pressure, and the required reforming rate cannot exceed 90%. (B) is a comparison of the gas composition at the inlet and the outlet of the adiabatic reformer 18. It can be seen that the reforming rate is high (about 80%) despite the low methane concentration. This is because, as described above, the ratio of water vapor to CH ₄ is very large (about 45) and the temperature of the anode exhaust gas is high (for example, about 680 ° C.). Further, under these conditions, the anode gas recycle line 1
By recirculating the anode exhaust gas through 6
As shown in (C), the overall reforming rate can be increased to 90% or more.

FIG. 2 is a characteristic diagram of the high-pressure fuel cell power generation equipment of the present invention. In this figure, the horizontal axis indicates the amount of recirculated gas, and the vertical axis indicates the overall reforming rate. Recirculated gas volume is 0
In the case of (zero), from Table 1 (A), the overall reforming rate is the reforming rate by the plate reformer alone (about 75%). Also, since there is no methane reaction in the fuel cell,
If the entire amount of the anode exhaust gas is supplied to the adiabatic reformer 18 and its reforming rate is about 80%, the overall reforming rate is 75+ (100−75) × 0.8 = 95%.
Therefore, as the amount of recirculated gas increases, the overall reforming rate increases by 95%.
%, And when the amount of recirculated gas is set to about twice the discharge amount, an overall reforming rate of about 90% can be achieved as described above.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0028]

As described above, the anode gas recycle line for recirculating a part of the anode exhaust gas discharged from the fuel cell to the anode side inlet of the fuel cell is provided, and the line is provided with a heat insulating catalyst having a reforming catalyst therein. By installing the reformer, the reforming reaction can be promoted by the sensible heat of the high-temperature anode exhaust gas itself in the adiabatic reformer. Therefore, under high pressure (for example, 10 ata or more), high reforming efficiency can be obtained as a whole of the power generation equipment. Furthermore, the hydrogen generated by the reforming is directly recycled through the anode gas recycling line to the anode side inlet of the fuel cell, so that the amount of hydrogen supplied to the fuel cell is increased, thereby increasing the power generation efficiency under high pressure. Can be enhanced.

Therefore, the high-pressure fuel cell power generation equipment of the present invention can be used without increasing the operating temperature of the plate reformer.
Under a high pressure equal to or more than ata, high reforming efficiency can be obtained as a whole of the power generation equipment, and thereby high power generation efficiency can be maintained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a high-pressure fuel cell power generation facility according to the present invention.

FIG. 2 is a characteristic diagram of the high-pressure fuel cell power generation equipment of the present invention.

FIG. 3 is a schematic configuration diagram of a conventional reformer.

FIG. 4 is a principle view of a conventional plate reformer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel gas 2 Source gas (process gas) 3 Reforming catalyst 4 Reforming gas 5 Combustion catalyst 6a-6e External manifold 7 Combustion air 8 Combustion gas 9 Steam 10 High pressure fuel cell power generation equipment 12 Reformer (plate reformer) 14 Fuel cell 16 Anode gas recycling line 17 Recycle blower 18 Insulated reformer

Claims (3)

[Claims] 1. In a fuel cell power generation facility for supplying a reformed gas reformed by a reformer to an anode side of a fuel cell, a part of anode exhaust gas discharged from the fuel cell is recirculated to an anode side inlet of the fuel cell. A high-pressure fuel cell power generation facility, comprising: an anode gas recycling line to be operated; and an adiabatic reformer installed in the line and having a reforming catalyst therein. 2. The high-pressure fuel cell power generation facility according to claim 1, further comprising a recycle blower for pressurizing and sending the anode exhaust gas to the anode gas recycle line. 3. The reformer is a plate reformer in which a flat reforming chamber Re and a heating chamber H are alternately stacked.
The high-pressure fuel cell power generation equipment according to claim 1 or 2, wherein: