JPS59105275A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To protect a low temperature shift converter or a fuel cell by arranging an analyzer detecting carbon monoxide concentration in the downstream of a high temperature shift converter and converting the passage of fuel gas to by-pass passage with a signal of the analyzer. CONSTITUTION:Mixed gas A is supplied to a reformer 2 to form gas B containing hydrogen and carbon monoxide and gas B is supplied to a high temperature shift converter 4 and concentration of residual carbon monoxide is remarkably reduced through a low temperature shift converter 4', then gas is supplied to a fuel electrode 1. A by-pass passage E is set in the downstream of the high temperature shift converter 4, and valves 6 and 7 are controlled with an analyzer 5 which detects the amount of residual carbon monoxide to convert the passage to the cell 1 and the by-pass passage E. Even when the reformer 2 or the high temperature shift converter 4 are unstablly operated in an unsteady stage such as starting or stop, performance deterioration or breakage of the low temperature shift converter 4' or cell 1 is effectively prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fuel cell power generation system provided with a mechanism for protecting a low temperature shift converter and a fuel cell during fuel cell operation.

[Technical background of the invention]

FIG. 1 shows a 4fr diagram of a conventional fuel cell power generation system.

Hydrogen is supplied to the fuel cell 1 as a fuel gas, and this fuel gas is passed through a reformer 2, a high temperature shift converter 4,
It is supplied through a low-temperature shift converter 4''k.A mixed gas A whose main components are fuel gas and water vapor is supplied to the reformer 2, which also contains hydrogen, carbon monoxide, etc. It is reformed into gas B and sent to the high temperature shift converter 4.

In high-temperature shift converter 4, most of the carbon monoxide contained in reformed gas B is converted into carbon dioxide and hydrogen to produce hydrogen-rich gas B, which contains even more hydrogen than reformed gas B. ' is sent to the low-temperature sint converter 4'. In this low-temperature shift converter 4', residual carbon oxide in the hydrogen-rich gas B' is converted into carbon dioxide and hydrogen, so that the concentration of residual carbon oxide is reduced to several percent or less. In this way, the low temperature shift converter 4'
The fuel gas C that has exited the fuel cell 1 is supplied to the fuel cell 1, where it comes into contact with air separately supplied from a route X to generate electricity. Air passes through the fuel cell 1 from path X and is discharged to path Y.

On the other hand, the fuel gas used for power generation is discharged from the fuel cell 1 and supplied to the reformer burner 3 through a route, where it is mixed with air separately supplied from a route 2 and combusted. The heat necessary for reforming the mixed gas A is supplied to the reformer 2.The reason for reducing the carbon monoxide concentration in the fuel gas C discharged from the low temperature shift converter 4' to below a few percent is to , - This is to prevent carbon oxide from poisoning the downstream electrode catalyst of the fuel cell 1 and reducing the catalytic activity.

In both the high-temperature shift converter 4 and the low-temperature shift converter 4', a reaction of CO+H20#CO2+H2 occurs, and carbon dioxide and hydrogen are generated from the carbon oxide and water vapor, and reaction heat is generated at this time.

Also, high temperature shift converter 4 and low temperature shift converter 4
The high temperature shift converter 4 is filled with a reaction catalyst to quickly carry out the above reaction, and the low temperature shift converter 4 is filled with a catalyst that has low activity but is inexpensive and suitable for large-scale processing. Although expensive, catalysts with high activity and suitable for small-scale processing are used.

[Problems with background technology]

In such a conventional fuel cell power generation system, the reaction conditions of the reformer 2 and the high temperature shift converter 4 are not stable during startup, shutdown, abnormality, etc., so that the amount of carbon monoxide exceeding the carbon monoxide processing capacity of the low temperature shift converter 4' is unstable. When fuel gas containing carbon monoxide is supplied to the low temperature shift converter 4', the reaction proceeds rapidly because the low temperature shift converter 4' uses a highly active catalyst, causing sudden heat generation. This may damage the catalyst or, in extreme cases, destroy the low temperature shift converter 4' itself.

In order to prevent such a situation, in the conventional fuel cell power generation system, the mixed gas A of fuel gas and water vapor supplied to the reformer 2 is reduced, and the low temperature shift converter 4'
The only options available were to reduce the amount of carbon monoxide supplied to the cryogenic sink converter 4' or to cool the low-temperature sint converter 4' itself.

Such a method is essentially a low temperature shift converter 4'
This has the disadvantage that the fuel cell 1 cannot be maintained sufficiently.

[Purpose of the invention]

An object of the present invention is to effectively maintain the relationship between a low temperature shift converter and a fuel cell even when the concentration of carbon monoxide, which causes a decrease in the performance of a catalyst constituting a low temperature shift converter and a fuel cell, increases. Our goal is to provide fuel cell power generation systems.

[Summary of the invention]

In order to achieve the above object, this invention comprises a high-temperature shift converter that converts most of the carbon monoxide in the fuel gas supplied through the reformer into carbon dioxide, and this high-temperature converter. a low-temperature shift converter that converts residual carbon oxide in the fuel gas into carbon dioxide and supplies it to the fuel cell as a hydrogen-rich gas containing carbon monoxide below a permissible value; a gas outlet of the high-temperature shift converter; A fuel cell power generation system comprising a connecting flow path connecting a gas inlet of a shift converter, a gas analyzer for detecting the amount of residual carbon oxide, and a bypass flow path branching off the connecting flow path. , gas switching means for switching the fuel gas flowing through the connecting flow path to the bypass flow path, and responding to the output signal of the gas analyzer when the amount of the residual carbon oxide exceeds a certain value. The gas switching means is operated to cause the fuel gas to flow into the bypass flow path.

[Embodiments of the invention]

The present invention will be described in detail below based on examples.

FIG. 2 is a configuration diagram of a fuel cell power generation system showing an embodiment of the present invention. In the following drawings, the same parts as shown in FIG. 1 are given the same reference numerals, and their explanations will be omitted.

In the conventional power generation system, nothing was installed in the connecting flow path connecting the high temperature shift converter 4 and the low temperature shift converter 4', but in the embodiment shown in Fig. 32, this connecting flow path was installed. A bifurcated pi-q gas flow path E and a gas analyzer 5 located in this connecting flow path to detect the amount of residual carbon in the exhaust gas from the high temperature shift converter 4 are provided. A valve 6 and a valve 7 are provided to switch between the flow path and the bypass flow path E.

With this configuration, according to the signal from the gas analyzer 5 installed downstream of the high-temperature shift converter 4, the fuel gas is normally supplied to the low-temperature shift converter 4' by opening the valve 6 and closing the valve 7. However, in the event of an abnormality, the valve 6 is closed in response to the output signal of the gas analyzer 5, and the valve 7 is opened to bypass the fuel gas to the bypass passage E.

The opening and closing operations of the valves 6 and 7 are linked, and when one is open, the other is closed. The opening/closing signals for the valves 6 and 7 are generated when the gas analyzer 5 detects the amount of carbon monoxide in the fuel gas B' and this detected value exceeds a certain value. Here, the constant value is a carbon monoxide concentration that is undesirable in maintaining the characteristics of the low temperature shift converter 4' and the fuel cell 1.

FIG. 3 is a block diagram showing another embodiment of the present invention.

This embodiment differs from the embodiment shown in FIG. 2 in that a structure 8 is inserted into the bypass channel E. This structure 8 has a predetermined flow path volume and flow path resistance. It is set to be equal to that when fuel gas flows through. By inserting such a structure 8 into the flow path E, it is possible to minimize pressure fluctuations when switching the flow path.
The chopsticks can be constructed by combining a container with nine valves and a volume element.

FIG. 4 is a block diagram showing still another embodiment of the present invention. In place of the valves 6 and 7 used in FIGS. 2 and 3, a three-way valve 9 is provided at the branching point between the connecting flow path and the pinose flow path, and this three-way valve 9 is used as the output of the gas analyzer 5. It is designed to switch in response to a signal, and its operation is similar to the cases shown in FIGS. 2 and 3, depending on whether fuel gas B' discharged from the high temperature shift converter 4 flows to the low temperature shift converter 4' or not. An operation is performed to selectively switch whether the flow is to the path E or not.

〔Effect of the invention〕

As described above in detail based on the embodiments, the present invention includes a gas analyzer that detects the carbon monoxide concentration in the fuel gas discharged from the high-temperature shift converter, and a A gas switching means is provided to switch the fuel gas flow path from the fuel cell flow path to the bypass flow path, so the reformer can be easily used when the power generation system is started, stopped, unsteady, abnormal, etc. Also, even if the carbon monoxide concentration in the fuel gas increases due to unstable operation of the high temperature shift converter, it has the advantage of being able to prevent characteristic deterioration or destruction of the low temperature shift converter or fuel cell due to this.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of a conventional fuel cell power generation system.
FIG. 2, FIG. 3, and FIG. 4 are block diagrams showing embodiments of the present invention, respectively. DESCRIPTION OF SYMBOLS 1... Fuel cell, 2... Reformer, 4... High temperature shift converter, 4'... Low temperature shift converter, 5...
...Gas analyzer, 6...Valve, 7...Valve, 8...Structure.

Claims (1)

[Claims] 1. A high-temperature shift converter that converts most of the carbon monoxide in the fuel gas supplied via the reformer into carbon dioxide, and the fuel supplied from the high-temperature converter. a low-temperature shift converter that converts residual carbon oxide in the gas into carbon dioxide and supplies it to the fuel cell as a hydrogen-rich gas containing carbon monoxide below a permissible value; a gas discharge port of the high-temperature shift converter; A fuel cell power generation system comprising a connecting flow path connecting to a gas inlet, a gas analyzer for detecting the amount of residual carbon oxide, a bypass flow path branching the connecting flow path, and the connecting flow path. gas switching means for switching the fuel gas flowing through the flow path to the nonopath flow path, and responding to the output signal of the gas analyzer when the amount of the residual carbon oxide exceeds a certain value. The fuel cell power generation system is characterized in that the fuel gas is caused to flow into the bypass flow path by operating the gas switching means. 2. The fuel cell power generation system according to claim 1, in which the gas switching means includes a first on-off valve provided in the connecting flow path and a first on-off valve provided in the bypass flow path and A fuel cell power generation system 3 characterized in that the fuel cell power generation system comprises a second on-off valve that operates in conjunction with an on-off valve, and a fuel cell power generation system according to claim 1, wherein the gas switching means A fuel cell power generation system comprising a three-way valve provided at a branch point between a flow path and the Nonoi Pass flow path. 4. In the fuel cell power generation system as set forth in claim 1, the Pi/Rs flow path includes a host body having a desired flow path volume and flow path resistance in the flow path. fr:
Characteristic fuel cell power generation system 0