JPH07192746A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a carbon monoxide transformed cata lyst to steadily operate for a long time by installing a hydrogen storage con tainer in which a hydrogen storage alloy is incorporated and adding hydrogen stored to hydrocarbon fuel during normal operation for desulfurization. CONSTITUTION:Hydrocarbon fuel 1 is mixed with a fuel gas whose main component is hydrogen introduced from a carbon monoxide transformer 6 and introduced into a hydrogenating-desulfurizing device 2. A hydrogenating-desulfurizing catalyst such as a No-Co base catalyst carried on alumina is filled in the hydrogenating-desulfurizing device 2, and an organic sulfur component in the hydrocarbon fuel 1 reacts with hydrogen and converted into hydrogen sulfide. The hydrocarbon fuel 1 is introduced into a desulfurizing device 3 in which a adsorbing-desulfurizing agent such as ZnO is filled, and the hydrogen sulfide generated is adsorbed in the adsorbing-desulfurizing agent to desulfurize the hydrocarbon fuel 1. The hydrocarbon fuel 1 desulfurized is mixed with steam supplied from a steam generator 4 and introduced into a steam reformer 5 in which a reforming pipe 6 filled with a reforming catalyst 7 such as a nickel base catalyst carried on alumina is arranged and converted into fuel gas whose main component is hydrogen by a steam reforming reaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system. More specifically, the hydrocarbon fuel can be desulfurized even at startup, and the carbon monoxide shift catalyst in the carbon monoxide shift converter can be protected even if the reforming catalyst is destroyed and scattered to the gas downstream side. And a fuel cell power generation system.

[0002]

2. Description of the Related Art In recent years, various alternative energies have been studied with the exhaustion of petroleum resources. As one of them, a fuel cell using hydrogen as a fuel for power generation has been attracting attention. This fuel cell consists of a fuel electrode and an oxidant electrode, supplies hydrogen to the fuel electrode and oxygen to the oxidant electrode, and contacts them through the electrolyte layer to take out electrical energy generated by an electrochemical reaction from both electrodes. It was done like this.

In this type of fuel cell, hydrogen is used as a fuel, and this hydrogen is generally used for steam reforming a hydrocarbon fuel such as natural gas, naphtha, liquefied petroleum gas, etc. It can be obtained by converting the fuel gas to

The above-mentioned hydrocarbon fuel contains an organic sulfur compound, and this sulfur component is adsorbed on the surface of the steam reforming catalyst and poisoned, which causes a significant decrease in the activity of the catalyst. Therefore, the hydrocarbon fuel is desulfurized by the desulfurization device before being supplied to the steam reformer.

Conventionally, a desulfurization method carried out before steam reforming of a hydrocarbon fuel is the presence of an Mo-Co type catalyst supported on alumina, which decomposes organic sulfur by adding hydrogen to produce hydrogen sulfide. It is a hydrodesulfurization method in which ZnO or the like is adsorbed and removed.

FIG. 3 is a schematic system diagram showing a typical example of a fuel cell power generation system equipped with a desulfurization device by a hydrodesulfurization method. In FIG. 3, the hydrocarbon fuel 1 is mixed with a fuel gas containing hydrogen as a main component, which is introduced from a carbon monoxide shift converter 9 described later, and is introduced into a hydrodesulfurizer 2. The hydrodesulfurizer 2 is filled with a hydrodesulfurization catalyst such as an alumina-supported Mo—Co-based catalyst, and the organic sulfur component in the hydrocarbon fuel 1 reacts with hydrogen and changes to hydrogen sulfide. afterwards,
The hydrogen sulfide generated by being introduced into the desulfurizer 3 filled with an adsorbent desulfurizing agent such as ZnO is adsorbed by the adsorbent desulfurizing agent, and the hydrocarbon fuel 1 is desulfurized.

The desulfurized hydrocarbon fuel 1 is mixed with the steam from the steam generator 4, and steam reforming is provided in which a reforming pipe 6 filled with a reforming catalyst 7 such as an alumina-supported Ni-based catalyst is provided. It is introduced into the vessel 5 and converted into a fuel gas containing hydrogen as a main component by a steam reforming reaction. The converted fuel gas is
Although hydrogen is the main component, it also contains carbon monoxide as a by-product. This carbon monoxide is the fuel electrode of the fuel cell body 10.
In order to poison the catalyst of No. 11, it is converted into carbon dioxide introduced into the carbon monoxide shift converter 9 filled with the carbon monoxide shift catalyst. A part of the fuel gas discharged from the carbon monoxide shift converter 9 is sent to the hydrodesulfurizer 2 as described above, and the rest is sent to the fuel electrode 11 of the fuel cell main body 10 to be used as a fuel. Hydrogen in the fuel gas flowing into the fuel electrode 11 causes an electrochemical reaction with oxygen in the air 14 being sent to the oxidant electrode 12 by the compressor 13, and as a result, the fuel gas is consumed and electric energy is consumed. You get 15.

[0008]

However, in such a fuel cell power generation system, there is a problem in the desulfurization process of hydrocarbon fuel. That is, in the hydrodesulfurization process, the supply of hydrogen is an essential condition, but since the steam reforming reaction occurs at startup, there is no supply of hydrogen, and since organic sulfur is not converted to hydrogen sulfide, it is also adsorbed in the desulfurizer. Instead, the hydrocarbon fuel is supplied to the steam reformer without being desulfurized. As a result, the organic sulfur in the hydrocarbon fuel is adsorbed by the reforming catalyst at the inlet of the reforming pipe, and the catalytic activity is significantly reduced.
Due to the nature of the fuel cell power generation system, starting and stopping are repeated every day, so the amount of sulfur components adsorbed on the reforming catalyst gradually increases, and the performance of the steam reformer, and thus the performance of the entire system, increases. There is a problem that the fuel cell power generation system deteriorates and cannot be stably operated for a long time.

Further, although the reforming catalyst is made of a ceramic solid, the fuel cell has a large number of start and stop times, and therefore the thermal expansion and contraction of the reforming tube occur frequently, and the reforming tube is repeatedly stressed. Therefore, the reforming catalyst in the reforming tube is destroyed by this stress, and finally powdered. When pulverization occurs, the gas will be scattered downstream. The scattered reforming catalyst flows into the carbon monoxide shift converter, is deposited on the carbon monoxide shift catalyst filled in the converter, and induces a metathesis reaction as shown in equation (1).

[0010]

## EQU1 ## CO + 3H ₂ ═CH ₄ + H ₂ O (1) The metalation reaction is a large exothermic reaction, and causes the heat deterioration of the carbon monoxide shift catalyst. As a result, the carbon monoxide metamorphic ability is reduced, and high concentration carbon monoxide flows into the fuel electrode of the fuel cell body, poisons the catalyst of the fuel electrode, and shortens the cell life. Further, the methanol reaction returns H ₂ in the fuel gas reformed by the reverse reaction of the reforming reaction in the cooking vessel to methane as a raw material, so that the yield of H ₂ is lowered and it is necessary for power generation. There is a problem that the amount of H ₂ cannot be secured.

The present invention has been made to solve the above-mentioned problems, and enables stable operation for a long time by supplying hydrogen for hydrodesulfurization even at the time of starting. It is an object of the present invention to provide a fuel cell power generation system capable of achieving the above.

Another object of the present invention is to provide a mesh-shaped permanent catalyst installed upstream of the carbon monoxide shifter even if the reforming catalyst is destroyed by repeated start-up and stop, pulverized and carried with gas and scattered downstream. The reforming catalyst collector filled with magnets collects the pulverized reforming catalyst to prevent the occurrence of a methanation reaction and the deterioration of the carbon monoxide shift catalyst in the carbon monoxide shift converter, thus ensuring a long time. Another object of the present invention is to provide a fuel cell power generation system that can be operated stably.

[0013]

In order to solve the above-mentioned problems, a fuel cell power plant according to the present invention supplies hydrogen to a hydrocarbon fuel at the time of starting, as described in claim 1, It is designed so that hydrodesulfurization can be performed. That is, a desulfurizer, a steam generator, a steam reformer, a carbon monoxide shift converter, a fuel cell main body, and the like are sequentially connected to form a system, and a hydrocarbon fuel is hydrodesulfurized by recycle addition of generated hydrogen, In a fuel cell power generation system in which steam is added and supplied to a reformer, where hydrogen is generated, and this hydrogen is supplied to a fuel cell and reacted with oxygen to extract electric energy, after the carbon monoxide transformer The flow is provided with a stop valve, a cooler for cooling the fuel gas and a hydrogen storage alloy, and a hydrogen storage device equipped with an electric heater for heating, and a flow control valve is provided downstream of the hydrogen storage device. Further, at the time of start-up, when supplying hydrogen to the hydrocarbon fuel, a control device is provided which gives an opening / closing signal to the flow rate control valve so that the hydrogen concentration in the hydrocarbon fuel becomes an optimum value.

Further, in order to solve the above-mentioned problems, the fuel cell power plant according to the present invention is characterized in that, even if the reforming catalyst is destroyed, pulverized and scattered, the carbon monoxide converter By equipping the reforming catalyst collector on the upstream side, the carbon monoxide shift catalyst in the carbon monoxide shift converter is protected. That is, a desulfurizer, a steam generator, a steam reformer, a carbon monoxide shift converter, a fuel cell main body, etc. are sequentially connected to form a system, and hydrogen is supplied to a fuel cell to react with oxygen to generate electrical energy. In the fuel cell power generation system that takes out the gas, a reforming catalyst collector filled with mesh-shaped permanent magnets is installed between the steam reformer and the carbon monoxide shifter, and the reforming catalyst becomes the carbon monoxide shifter. It is characterized in that it is possible to measure the degree of collection of the reforming catalyst by providing a collector differential pressure gauge while preventing the inflow, and thereby to know the remaining amount of the reforming catalyst in the reforming pipe.

[0015]

In the present invention, during normal operation of the fuel cell power generation system, the stop valve at the downstream of the carbon monoxide shift converter is opened to allow the fuel gas to flow in. The inflowing gas is cooled to room temperature by a cooler, and then introduced into a hydrogen storage device to cause the hydrogen storage alloy to occlude hydrogen as a main component in the fuel gas.

On the other hand, at the time of start-up, the stop valve is closed and the flow control valve is opened, and the hydrogen is heated by an electric heater built in the hydrogen storage device to release the hydrogen stored in the hydrogen storage alloy during normal operation. Add to hydrogen fuel. The amount of hydrogen added to the hydrocarbon fuel is measured with a flow meter provided at the inlet of the hydrodesulfurizer and the flow control valve, and the amount of hydrogen added is controlled to be 2% by volume of the flow rate of the hydrocarbon fuel. It is controlled by adjusting the opening of the control valve in the device.

Therefore, hydrogen can be supplied to the hydrocarbon fuel and hydrodesulfurization can be performed even when the steam reformer is not operating. For destruction and pulverization of the reforming catalyst due to repeated start and stop, even if the pulverized catalyst is carried along with the fuel gas and flows out from the steam reformer, the reforming catalyst is a Ni-based ferromagnetic material. , And can be prevented from being collected by the mesh-shaped permanent magnets filled in the reforming catalyst collector and accumulated on the downstream side carbon monoxide transformer.

Further, since it is equipped with a collector differential pressure gauge,
It is possible to know the remaining amount of reforming catalyst in the reforming pipe during operation,
This makes it possible to grasp the reforming state during the operation of the steam reformer.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a fuel cell power generation system according to an embodiment of the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals. Reference numeral 1 shown in FIG.
A hydrocarbon fuel, which is a hydrocarbon fuel 1, is mixed with a fuel gas containing hydrogen as a main component, which is introduced from a carbon monoxide shift converter 6 described later, and is introduced into a hydrodesulfurizer 2. The hydrodesulfurizer 2 is filled with a hydrodesulfurization catalyst such as an alumina-supported Mo—Co-based catalyst, and the organic sulfur component in the hydrocarbon fuel 1 reacts with hydrogen and changes to hydrogen sulfide. Then Z
Hydrogen sulfide produced by being introduced into the desulfurizer 3 filled with an adsorbent desulfurizing agent such as nO is adsorbed by the adsorbent desulfurizing agent, and the hydrocarbon fuel 1 is desulfurized.

The desulfurized hydrocarbon fuel 1 is mixed with the steam from the steam generator 4, and steam reforming is provided in which a reforming pipe 6 filled with a reforming catalyst 7 such as a Ni-based catalyst supported on alumina is provided. It is introduced into the vessel 5 and converted into a fuel gas containing hydrogen as a main component by a steam reforming reaction. The converted fuel gas is
Although hydrogen is the main component, it also contains carbon monoxide as a by-product. This carbon monoxide is the fuel electrode of the fuel cell body 10.
In order to poison the 11 catalyst, it is introduced into the carbon monoxide shift converter 9 filled with the carbon monoxide shift catalyst and converted into carbon dioxide. The fuel gas discharged from the carbon monoxide transformer 9 is
A part is sent to the hydrodesulfurizer 2 as described above, and the rest is sent to the fuel electrode 11 of the fuel cell body 10 and used as a fuel.
Hydrogen in the fuel gas flowing into the fuel electrode 11 causes an electrochemical reaction with oxygen in the air 14 being sent to the oxidant electrode 12 by the compressor 13, and as a result, the fuel gas is consumed and electric energy is consumed. You get 15.

On the other hand, during the above operation, the carbon monoxide transformer 9
The stop valve 16 provided on the downstream side is opened to allow the fuel gas to flow in. After the inflowing fuel gas is cooled to room temperature by the cooler 17, it is introduced into the hydrogen storage device 18, and the hydrogen storage alloy 19 stores hydrogen as the main component in the fuel gas.

However, at the time of start-up, the stop valve 16 is closed, the flow control valve 21 provided in the downstream of the hydrogen storage 18 is opened, and the electric heater 20 built in the hydrogen storage is used for heating to perform normal operation. The hydrogen stored in the hydrogen storage alloy 19 is released and added to the hydrocarbon fuel 1. The amount of hydrogen added to the hydrocarbon fuel 1 is adjusted as follows so as to be 2% by volume of the flow rate of the hydrocarbon fuel. That is, the flow rate of hydrocarbon fuel is measured by the flow meter 22 provided at the inlet of the hydrodesulfurizer 2, and the flow rate of hydrogen is measured by the flow meter 23 provided downstream of the flow rate control valve 21. The flow rate signal of each flow meter is transmitted to the control device 24, and the flow rates of the both are compared. An output signal 25 from the control device 24 so that the hydrogen flow rate becomes 2% by volume according to the hydrocarbon fuel flow rate.
Thus, the opening degree of the flow rate control valve 23 is adjusted. The hydrocarbon fuel 1 to which 2% by volume of hydrogen has been added is desulfurized by the desulfurizer as in the above-described operation.

Thus, the amount of hydrogen in the hydrocarbon fuel 1 is 2
Adjust the flow rate control valve 21 opening so that the volume% is reached.
By adjusting the hydrogen flow rate from 18 and adding it to the hydrocarbon fuel 1, hydrogen can be made to exist in the hydrocarbon fuel 1 even at the time of starting. As a result, the steam reformer 5
Is not operating and therefore hydrogen is added to the hydrocarbon fuel 1 even at the time of starting without hydrogen, so that the organic sulfur in the hydrocarbon fuel 1 is converted into hydrogen sulfide in the hydrodesulfurizer 2. Then, since the hydrogen sulfide converted in the desulfurizer 3 is adsorbed, the desulfurized hydrocarbon fuel 1 is converted into the steam reformer 5
It is possible to prevent the sulfur component from being adsorbed to the reforming catalyst 7 introduced into the reforming pipe 6 and filled in the reforming pipe 6.

FIG. 2 shows another embodiment of the fuel cell power generation system according to the present invention. The same devices and parts as those in FIG. 3 are designated by the same reference numerals. Reference numeral 1 shown in FIG. 2 is a hydrocarbon fuel, which is sequentially introduced into the hydrodesulfurizer 2 and the desulfurizer 3 to remove the sulfur component in the hydrocarbon fuel. Hydrocarbon fuel from which sulfur components have been removed 1
Is introduced into the steam reformer 5 in which the reforming pipe 6 filled with the reforming catalyst 7 is mixed with the steam from the steam generator 4. The reforming catalyst 7 in the reforming tube 6 is mainly composed of ferromagnetic metal particles supported on alumina, and the hydrocarbon fuel is converted into a fuel gas containing hydrogen as a main component by a steam reforming reaction. . Then, the reformed fuel gas is used as a reforming catalyst collector.
26 and the carbon monoxide shift converter 9 are sequentially sent to the fuel electrode 11 of the fuel cell body 10. Further, the oxygen of the oxidizer electrode 12 of the fuel cell main body 10 is supplied by sending air 14 through the compressor 13. As a result, an electrochemical reaction in which water is synthesized from hydrogen and oxygen is performed in the fuel cell main body 10, the chemical energy is directly converted into electrical energy and power generation occurs, and electrical energy-15 is obtained.

During operation of the fuel cell, the steam reformer 5
The temperature of the reforming pipe 6 installed inside the
The temperature rises from 00 ° C to 1000 ° C and the reforming pipe 6 expands.
When stopped, the temperature of the reforming pipe 6 becomes room temperature, and the reforming pipe 6 contracts as compared with during operation. By repeating this expansion and contraction, mechanical reforming stress is applied to the reforming catalyst 7 in the reforming pipe 6, and it is destroyed and pulverized and scattered toward the gas downstream side. Even if the reformed catalyst 7 that has scattered is discharged from the steam reformer 5, since it is a Ni-based ferromagnetic material, it is collected by the mesh-shaped permanent magnets filled in the reforming catalyst collector 26. Also,
During operation, the differential pressure of the reforming catalyst collector 26 is measured by the collecting differential pressure gauge 27, and the amount of the reforming catalyst 7 collected is monitored. When the differential pressure measurement value exceeds a certain value, an alarm signal (not shown) automatically stops the fuel cell power generation system. This is because the amount of the reforming catalyst in the reforming pipe 6 decreases, the conversion rate of the hydrocarbon fuel 1 to the fuel gas decreases, and the hydrogen supply amount to the fuel electrode becomes insufficient. Because you cannot do it. By equipping this reforming catalyst collector 26, not only the protection of the carbon monoxide shift converter 9 but also the damage of the fuel cell main body 10 can be prevented beforehand.

[0026]

As described above, in the present invention, the hydrogen stored in the hydrogen storage alloy during normal operation can be added to the hydrocarbon fuel at the start-up when hydrogen is not generated. Therefore, even at the time of start-up, the hydrodesulfurizer and the desulfurizer are effectively operated, and the organic sulfur in the hydrocarbon fuel is desulfurized and introduced into the steam reformer. Therefore,
Activity deterioration due to adsorption of the sulfur component of the reforming catalyst is prevented, the fuel cell power generation system can be stably operated for a long time, and it contributes to improvement of power generation efficiency.

Further, since the reforming catalyst can maintain a high activity for a long time, a high SV (Space Velocity) operation can be performed, and the apparatus can be downsized and the catalyst cost can be reduced. Furthermore, due to repeated expansion and contraction, the reforming catalyst in the reforming pipe is destroyed by mechanical force and scattered into powder, and the scattered reforming catalyst is scattered to the downstream side of the gas. And the deterioration of the carbon monoxide shift catalyst due to the metalation reaction that has occurred in the carbon monoxide shift converter,
It is possible to prevent a decrease in hydrogen yield. In addition, the amount of reforming catalyst remaining in the reforming pipe can also be known by installing a collector differential pressure gauge, and the reforming state of the steam reformer can also be ascertained by this. An appropriate amount of hydrogen can be supplied to the main body, the fuel cell main body can be extended without causing damage, and long-term stable operation can be achieved.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a fuel cell power generation system according to the present invention.

FIG. 2 is a system diagram showing another embodiment of the fuel cell power generation system according to the present invention.

FIG. 3 is a system diagram showing a conventional fuel cell power generation system.

[Explanation of symbols]

1 ... Hydrocarbon fuel, 2 ... Hydrodesulfurizer, 3 ... Desulfurizer, 4 ...
Steam generator, 5 ... Steam reformer, 6 ... Reforming tube, 7 ... Reforming catalyst, 8 ... Burner, 9 ... Carbon monoxide shifter, 10 ... Fuel cell main body, 11 ... Fuel electrode, 12 ... Oxidant electrode, 13 ... Compressor, 14 ... Air, 15 ... Electric energy, 16 ... Stop valve, 17 ...
Cooler, 18 ... Hydrogen storage device, 19 ... Hydrogen storage alloy, 20 ... Electric heater, 21 ... Flow control valve, 22 ... Flow meter, 23 ... Flow meter, 24
... Control device, 25 ... Output signal, 26 ... Reforming catalyst collector, 27 ...
Collector differential pressure gauge.

Claims (2)

[Claims] 1. After desulfurizing a hydrocarbon fuel with a desulfurizer,
In a fuel cell power generation system in which steam is added and supplied to a steam reformer, where hydrogen is generated, and this hydrogen is supplied to a fuel cell and reacted with oxygen to extract electric energy, a hydrogen storage alloy is incorporated. A fuel cell power generation system comprising a hydrogen storage device, wherein hydrogen stored during normal operation is released at the time of startup and added to a hydrocarbon fuel for hydrodesulfurization. 2. After desulfurizing the hydrocarbon fuel with a desulfurizer,
In a fuel cell power generation system in which steam is added and supplied to a steam reformer, where hydrogen is generated, and this hydrogen is supplied to a fuel cell and reacted with oxygen to extract electric energy, a mesh-shaped permanent magnet is used. If the packed reforming catalyst collector is installed and the reforming catalyst is destroyed during normal operation and scatters to the gas downstream side, it is installed in the downstream by collecting with the reforming catalyst collector. A fuel cell power generation system characterized by protecting a carbon monoxide shift catalyst in a carbon oxide shift converter.