JPH1012256A - Fuel cell equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell equipment by which an inlet temperature of anode gas and cathode gas of a fuel cell can be controlled in a proper range without adding a heating system such as an electric heater and a piping heater and without separately controlling the temperature on the anode side and the cathode side not only at high load time but also at low load time and OCV (a connecting-disconnecting condition of an output circuit) time. SOLUTION: This equipment 20 has a heat exchanger 22 to exchange heat between anode gas 2 and cathode gas 3 on the upstream side of a fuel cell 11. Here, a temperature of the cathode gas 3 of an inlet of the fuel cell 11 is adjusted by a cathode circulating gas quantity, and a temperature of the anode gas 2 of the inlet of the fuel cell 11 is adjusted by heat exchange between the cathode gas 3 and the anode gas 2. The heat exchanger 22 is a partition wall type parallel flow heat exchanger, and is arranged closest to the upstream side of the fuel cell 11, and is housed in the same housing vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten carbonate fuel cell, and more particularly, to a fuel cell system capable of adjusting an inlet temperature of a fuel cell.

[0002]

2. Description of the Related Art In a power generation facility using a molten carbonate fuel cell that uses natural gas or the like as fuel (hereinafter, simply referred to as a fuel cell facility), as shown in FIG. A reformer 10 for reforming the anode gas 2 containing the fuel gas, and a fuel cell 11 for generating electricity from the anode gas 2 and the cathode gas 3 containing oxygen. After being supplied to the anode side A of the battery 11 and consuming most (for example, 80%) in the fuel cell, it is supplied as anode exhaust gas 4 to downstream equipment (for example, a combustion chamber of a reformer). On the other hand, in the reformer 10, the fuel gas 1 is reformed by heating the reforming pipe 10 a by burning the fuel gas, and the combustion exhaust gas 5 whose temperature is lowered by the endothermic heat of the reforming pipe 10 a is supplied to the outside. Is mixed with the air 6 supplied from the fuel cell and becomes the cathode gas 3 and supplied to the cathode side C of the fuel cell 11. Further, part of the cathode gas (cathode exhaust gas 7) partially reacted in the fuel cell 11 is circulated to the upstream side of the fuel cell 11 by the high-temperature blower 12, and the remainder is downstream equipment (for example, a turbine compressor or the like). Supplied to In this figure, reference numeral 12a denotes a gas heater.

[0003]

As described above, in the conventional fuel cell system, the reformed gas generated in the reformer 10 is directly introduced into the anode side A of the fuel cell 11 as the anode gas 2, On the cathode side C of the fuel cell 11, a mixture of the combustion exhaust gas 5 of the reformer 10 and the air 6 as an oxidant for the cell reaction is mixed with the high temperature cathode exhaust gas circulated by the high temperature Make adjustments,
It is sent to the cathode side C.

However, in the above-mentioned conventional fuel cell system, the inlet temperature tc on the cathode side can be easily adjusted by the circulation amount of the cathode gas by the high temperature blower 12, but it is difficult to adjust the inlet temperature ta on the anode side. There was a problem. Hereinafter, this will be described in detail.

FIGS. 4A and 4B show examples of the temperature distribution of each part in a conventional fuel cell system. FIG. 4A shows a high load (about 100% load), FIG. 4B shows a low load (about 30% load), and FIG. C) indicates a disconnected state (Open Circuit Voltage: OCV) of the output circuit. As shown in FIG. 4A, at a high load close to 100% load, the reformer outlet temperature of the anode gas 2 is about 6%.
30 ° C., which becomes about 610 ° C. due to heat radiation and flows into the fuel cell 11. On the other hand, the outlet temperature of the reformer on the cathode side is about 524 ° C., mixed with the air 6, mixed with the high temperature (about 630 ° C.) cathode exhaust gas, and flows into the fuel cell 11 at about 580 ° C. Therefore, at the time of high load (A),
The inlet temperature of both gases is adjusted to an appropriate range (for example, about 58
0-600 ° C).

On the other hand, when the load is low (B), the outlet temperature of the reformer of the anode gas 3 decreases (for example, about 584 ° C.). If the anode gas 3 is supplied to the fuel cell 11 as it is, the anode inlet temperature further decreases. . However, when the anode inlet temperature becomes, for example, about 550 ° C. or less, carbon deposition occurs on the anode side, which may seriously hinder power generation. for that reason,
In the conventional fuel cell equipment, as shown in FIG. 4B, an electric heater 13 and a pipe heater 14 are installed in an anode gas line between the reformer 10 and the fuel cell 11, whereby a battery for the anode gas 2 is provided. If the inlet temperature is within the appropriate range (eg, about 58
(0-600 ° C.). However, this requires not only the electric heater 13 and the pipe heater 14, but also a problem that it is necessary to separately control the temperature not only on the cathode side but also on the anode side.

Further, as shown in FIG. 4 (C), at the time of OCV, the air-fuel ratio on the combustion side of the reformer must be increased in order to secure a necessary amount of carbon dioxide on the cathode side (for example, low air-fuel ratio). About 1.7 times the load). For this reason, the amount of the combustion exhaust gas becomes excessive with respect to the amount of the reformed gas, and the outlet temperature of the reformer of the anode gas becomes high (for example, about 641
° C), the temperature difference from the cathode side increases, which may adversely affect the battery.

The present invention has been made to solve the above-mentioned problems. That is, an object of the present invention is to provide a fuel cell in which the inlet temperatures of the anode gas and the cathode gas of the fuel cell can be controlled within an appropriate range (for example, about 580 to 600 ° C.) not only at the time of high load but also at the time of low load and OCV. To provide facilities. Another object of the present invention is to provide an anode gas and cathode gas inlet for a fuel cell without adding a heating device such as an electric heater or a pipe heater, and without separately controlling the temperature on the anode side and the cathode side. An object of the present invention is to provide a fuel cell facility capable of controlling a temperature within an appropriate range.

[0009]

The inventor of the present invention has found that the flow rate of the cathode gas is much larger than that of the anode gas (for example, about 70 times). Was focused on being able to always approach the temperature of the cathode gas. The present invention is based on such a new finding.

That is, according to the present invention, a reformer for reforming a fuel gas to an anode gas containing hydrogen, a fuel cell for generating electricity from the anode gas and a cathode gas containing oxygen, and a cathode passing through the fuel cell A fuel circulation system having a cathode circulation line for circulating gas upstream of the fuel cell, further comprising a heat exchanger for exchanging heat between the anode gas and the cathode gas upstream of the fuel cell; Thus, the temperature of the cathode gas at the fuel cell inlet is adjusted, and the temperature of the anode gas at the fuel cell inlet is adjusted by heat exchange between the cathode gas and the anode gas.

According to the configuration of the present invention, the temperature of the cathode gas at the fuel cell inlet is merely adjusted to an appropriate range (for example, about 580 to 600 ° C.) by the amount of the circulating cathode gas.
The anode gas of the fuel cell can be used not only at high load, but also at low load and OCV without adding a heating device such as an electric heater or a pipe heater, and without separately controlling the temperature on the anode side and the cathode side. In addition, the inlet temperature of the cathode gas can be controlled in an appropriate range (for example, about 580 to 600 ° C.).

That is, at the time of a high load close to 100% load, as shown in FIG. 4A, the inlet temperature of both gases is adjusted only by adjusting the cathode gas inlet temperature by adjusting the amount of circulating cathode gas. (For example, about 580 to 600 ° C.). In this case, the anode inlet temperature is cooled by the cathode gas to an appropriate temperature, but slightly higher than the cathode gas.

Next, at a low load, as shown in FIG. 4B, the reformer outlet temperature drops to about 580 ° C.
Since there is no electric heater or pipe heater as in the related art, the heat exchanger inlet temperature is further reduced. However, the cathode gas inlet temperature is in an appropriate range (for example, about 580 to 600 ° C.), and the cathode gas amount is about 7 times the anode gas amount.
Since the flow rate is 0 times, the anode gas temperature is heated to a temperature substantially equal to the cathode gas temperature by the heat exchange in the heat exchanger. Therefore, the inlet temperature of both gases can be adjusted to an appropriate range (for example, about 580 to 600 ° C.) only by adjusting the inlet temperature on the cathode side to a higher value (for example, about 590 to 600 ° C.) within an appropriate range. .

Further, at the time of OCV, as shown in FIG. 4C, the outlet temperature of the reformer rises to about 640 ° C.,
Although the heat exchanger inlet temperature also becomes 600 ° C. or higher, the anode gas temperature is cooled to a temperature substantially equal to the cathode gas temperature by heat exchange with a large amount of cathode gas, contrary to the low load condition. Therefore, in this case as well, the inlet temperature on the cathode side is lowered within an appropriate range (for example, about 580 to 590 ° C.).
The inlet temperature of both gases can be adjusted to an appropriate range (for example, about 580 to 600 ° C.) only by adjusting

According to a preferred embodiment of the present invention, the heat exchanger is a partition type parallel flow heat exchanger, which is disposed immediately upstream of the fuel cell and stored in the same storage container. With this configuration, the pressure in the heat exchanger can be adjusted to the same pressure as the container pressure, the anode gas pressure, and the cathode gas pressure that are differentially controlled to the same pressure in the containment vessel without adding any control device. The pressure can be controlled, the differential pressure between the anode gas and the cathode gas in the heat exchanger can be suppressed, and the safety against gas leakage and the like can be improved.

Further, it is preferable that the heat exchanger is a gas header formed integrally with the fuel cell. With this configuration, the heat exchanger can be incorporated into the fuel cell,
The apparatus can be made compact and cost can be reduced.

[0017]

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 fuel cell facility according to the present invention. In this figure, a fuel cell system 20 of the present invention includes a reformer 10 for reforming a fuel gas 1 into an anode gas 2 containing hydrogen, and a fuel cell 11 for generating electricity from the anode gas 2 and a cathode gas 3 containing oxygen. And a cathode circulation line 1 for circulating the cathode gas passing through the fuel cell 11 to the upstream side of the fuel cell 11
5 is provided. The cathode circulation line 15 is provided with a high-temperature blower 12 and a gas heater 12a. Such a configuration is the same as that of the conventional fuel cell equipment shown in FIG.

The fuel cell equipment 20 of the present invention further includes a heat exchanger 22 for exchanging heat between the anode gas 2 and the cathode gas 3 on the upstream side of the fuel cell 11. This heat exchanger 2
Reference numeral 2 denotes a partition type parallel flow heat exchanger (for example, a plate fin heat exchanger), which is disposed immediately upstream of the fuel cell 11 and stored in the same storage container 11a. With this configuration, any control device for controlling the pressure in the heat exchanger 22 is added to the same pressure as the container pressure, the anode gas pressure, and the cathode gas pressure that are differentially controlled to the same pressure in the storage container 11a. The pressure difference between the anode gas 2 and the cathode gas 3 in the heat exchanger 22 can be suppressed, and the safety against gas leakage and the like can be improved.

The heat exchanger 22 may be a gas header formed integrally with the fuel cell 11, and the functions of the gas header and the heat exchanger may be used together. With this configuration,
The heat exchanger can be incorporated in the fuel cell, and the device can be reduced in size and cost.

The above-described fuel cell system 20 of the present invention operates as follows. First, by controlling the rotation speed of the high-temperature blower 12, the amount of the cathode circulating gas passing through the cathode circulating line 15 is changed, thereby adjusting the cathode gas temperature tc at the inlet of the fuel cell 11. This control method is the same as that of the conventional fuel cell equipment, but the temperature control range needs to be slightly strict as described later. Note that, in the fuel cell equipment of the present invention, the anode gas temperature is not directly controlled, but is indirectly adjusted by the heat exchange between the cathode gas and the anode gas, as described later.

Therefore, in the fuel cell system of the present invention, not only at the time of high load, but also at the time of low load and at the time of OCV, a heating device such as an electric heater or a piping heater is not added, and the anode side and the cathode side are used. Without separately controlling the temperature, the inlet temperatures of the anode gas and the cathode gas of the fuel cell can be controlled within an appropriate range (for example, about 580 to 600 ° C.).

FIG. 2 is a view similar to FIG. 4 showing the temperature of each part in the fuel cell equipment according to the present invention. In this figure, (A) shows a high load (about 100% load), (B) shows a low load (about 30% load), and (C) shows a disconnected state (OCV) of the output circuit.

At a high load close to 100% load, FIG.
As shown in (A), the inlet temperature of both gases can be adjusted to an appropriate range (for example, about 580 to 610 ° C.) only by adjusting the cathode side inlet temperature by the amount of circulating cathode gas. In this case, the anode inlet temperature is cooled by the cathode gas to an appropriate temperature, but slightly higher than the cathode gas.

Next, at a low load, as shown in FIG. 4B, the outlet temperature of the reformer drops to about 580 ° C., and since there is no electric heater or pipe heater as in the conventional case, the heat exchanger is not used. Although the inlet temperature is further lowered, the cathode gas inlet temperature is set in an appropriate range (for example, about 580 to 600 ° C.)
Further, since the amount of the cathode gas has a flow rate about 70 times the amount of the anode gas, the temperature of the anode gas is heated to a temperature substantially equal to the temperature of the cathode gas by heat exchange in the heat exchanger. Therefore, by merely adjusting the inlet temperature on the cathode side to a higher value (for example, about 590 to 600 ° C.) within an appropriate range, the inlet temperatures of both gases are adjusted to an appropriate range (for example, about 580 to 580 ° C.).
(600 ° C.).

Further, at the time of OCV, as shown in FIG. 4 (C), the reformer outlet temperature rises to about 641 ° C. and the heat exchanger inlet temperature rises to 600 ° C. or higher, but is opposite to that at low load. In addition, the anode gas temperature is cooled to a temperature substantially equal to the cathode gas temperature by heat exchange with a large amount of cathode gas. Therefore, also in this case, the inlet temperature of both gases is adjusted to a proper range (for example, about 580 to 600 ° C.) only by adjusting the inlet temperature on the cathode side to be lower (for example, about 580 to 590 ° C.) within a proper range. Can be adjusted.

It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various changes can be made without departing from the gist of the present invention.

[0027]

As described above, the fuel cell system of the present invention can be used not only under high load, but also under low load and OCV.
Without adding a heating device such as an electric heater or a pipe heater, and without separately controlling the temperature on the anode side and the cathode side, the inlet temperature of the anode gas and the cathode gas of the fuel cell can be adjusted to an appropriate range (for example, about 580 to 600 ° C).

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel cell facility according to the present invention.

FIG. 2 is a diagram showing the temperature of each part in the fuel cell equipment according to the present invention.

FIG. 3 is a configuration diagram of a conventional fuel cell facility.

FIG. 4 is a diagram showing the temperature of each part in a conventional fuel cell facility.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel gas 2 Anode gas 3 Cathode gas 4 Anode exhaust gas 5 Combustion exhaust gas 6 Air 7 Cathode exhaust gas 10 Reformer 10a Reforming tube 11 Fuel cell 11a Storage container 12 High temperature blower 12a Gas heater 13 Electric heater 14 Pipe heater 15 Cathode circulation line 20 Fuel cell equipment 22 Heat exchanger

Claims (3)

[Claims] 1. A reformer for reforming a fuel gas into an anode gas containing hydrogen, a fuel cell for generating electricity from the anode gas and a cathode gas containing oxygen, and a cathode gas passing through the fuel cell being upstream of the fuel cell. A fuel cell system having a cathode circulation line circulating on the fuel cell side, and further comprising a heat exchanger for exchanging heat between the anode gas and the cathode gas on the upstream side of the fuel cell. A fuel cell system, wherein the temperature of a cathode gas is adjusted, and the temperature of the anode gas at the fuel cell inlet is adjusted by heat exchange between the cathode gas and the anode gas. 2. The heat exchanger according to claim 1, wherein the heat exchanger is a partition type parallel flow heat exchanger, which is disposed immediately upstream of the fuel cell and stored in the same storage container. The fuel cell facility as described. 3. The fuel cell equipment according to claim 1, wherein the heat exchanger is a gas header formed integrally with a fuel cell.