JP2002124288A - Fuel cell power generation device and its starting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell power generation device capable of simplifying the structures of a CO reformer and a CO eliminator, and of reducing consumption power and a starting period in starting the power generation device and provide its starting method. SOLUTION: This fuel cell power generation device generates power by feeding a fuel gas provided by steam-reforming a hydrocarbonaceous raw fuel and an oxidizer gas to a fuel cell. In starting the fuel cell power generation device, feed water for steam generation heated by a combustion exhaust gas is passed to a reforming fed water recirculation line 1 with the combustion exhaust gas of a reformer 11 fed to a steam generator 14 to heat the CO reformer 12 and the CO eliminator 13, and after the temperatures of the CO reformer and the CO eliminator reach predetermined values, the passage of the feed water is changed over to a reforming steam feeding line 15 by shut-off valves 2 and 3, and the raw fuel supply to the steam generator 14 is stopped by closing a closing valve 5 of a raw fuel supply line 4.

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 generator for supplying fuel gas and oxidizing gas obtained by steam reforming raw fuel to a fuel cell to generate electric power, and a method of starting the fuel cell power generator.

[0002]

2. Description of the Related Art There are various types of fuel cells to be incorporated in a fuel cell power generator, depending on the type of electrolyte, the type of reforming material, and the like. As a fuel cell of a relatively low temperature of about 80 ° C., a solid polymer electrolyte fuel cell is well known.

[0003] This solid polymer electrolyte fuel cell is, like the phosphoric acid fuel cell, hydrogen in the fuel gas obtained by steam reforming a hydrocarbon-based raw fuel such as methane gas and oxygen in the air. Are supplied to the fuel electrode and the air electrode of the fuel cell, respectively, to generate power based on an electrochemical reaction.

In reforming raw fuel into fuel gas, a method of adding steam to raw fuel to promote reforming by a catalyst in a fuel reformer has been adopted. It is necessary to constantly replenish the required amount of steam, and it is necessary to constantly replenish the water supply device with the corresponding amount of water. The water used must be high-purity water, and ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment apparatus is generally used.

On the other hand, in the electrochemical reaction of the fuel cell, water generated by power generation is generated, and in the fuel reformer, the water generated by combustion is accompanied by combustion for heating the catalyst to perform a steam reforming reaction, which is an endothermic reaction, constantly. However, these generated waters have less impurities than ordinary tap water, and if these generated waters are used as raw water, the load on the water treatment equipment can be reduced. In addition, a method of recovering the generated water and using it as feed water for generating reformed steam is usually adopted.

FIG. 2 shows an example of a conventional solid polymer electrolyte fuel cell power generator using city gas as a raw fuel, and is a basic system diagram mainly focusing on a fuel reforming system.

In FIG. 2, a fuel cell 1 schematically shown
No. 0 is constituted by arranging and laminating a cooling plate (not shown) having a cooling pipe or a cooling groove every time a plurality of unit cells having the fuel electrode 10a and the air electrode 10b are stacked.

The raw fuel is first supplied to a reformer 11 together with steam for reforming, and is reformed into hydrogen and carbon monoxide by the following reaction.

CH ₄ + H ₂ O → 3H ₂ + CO (endothermic reaction) Thereafter, the reformed gas is supplied to a CO converter 12,
The following reaction reduces -carbon oxide in the reformed gas to about 1%.

CO + H ₂ O → H ₂ + CO ₂ (exothermic reaction) Thereafter, the gas is further supplied to a CO remover 13, and the carbon monoxide in the reformed gas is reduced to about 100 ppm by the following reaction. To the fuel electrode 10a.

CO + 1 / 2O ₂ → CO ₂ (exothermic reaction) As described above, when the reforming reaction is performed in the reformer 11,
It is necessary to supply steam, and in a polymer electrolyte fuel cell power generator, sensible heat of the combustion exhaust gas of the reformer 11 and reaction heat of the CO converter 12 and the CO remover 13 are generally used as heat sources. It is a target. Therefore, a reforming steam supply line 15 is provided for sequentially flowing the reforming water supplied by the pump through the reactors of the CO shift converter 12, the CO remover 13, and the steam generator 14 in series. Receiving heat from the reactor to produce steam, mixing this steam with raw fuel,
It is configured to be introduced into the reformer 11 from the reforming steam supply line 15.

Since each of the above-mentioned reactors performs a chemical reaction using a catalyst, it is necessary to raise the temperature to an appropriate temperature before starting the fuel cell power generator. The appropriate temperature for each reactor is as follows. Reformer: 500-700 ° C, CO converter: 200-300 ° C, CO remover: 100-250 ° C.

For this reason, the temperature of the reformer 11 is raised by burning the raw fuel by a burner installed in the reformer, and the temperature of the steam generator 14 is also raised by the combustion exhaust gas. . On the other hand, the CO converter 12 and the CO remover 13 are respectively provided with electric heaters 12a and 12a individually provided.
The temperature is raised by 3a.

[0014]

The above-mentioned conventional fuel cell power generator has the following problems.

When the temperature of the CO converter and the CO remover is increased by the electric heater at the time of starting, the internal catalyst cannot be sufficiently heated only by heating with a mantle beater or the like from the outside of each reactor. It is necessary to install a sheath heater or the like inside the layer. Therefore, in the catalyst layers of the CO shift converter and the CO remover, it is necessary to appropriately dispose both a heater for raising the startup temperature and a cooling pipe for preventing heating due to an exothermic reaction during normal operation. There was a problem that became complicated. Further, in order to shorten the start-up time, it is necessary to increase the heater capacity, and there has been a problem that excessive electric power is required at the time of start-up.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a CO transformer and a C transformer.
An object of the present invention is to provide a fuel cell power generator and a method for starting the fuel cell, which simplify the structure of the O remover, reduce power consumption at the time of starting the power generator, and shorten the start time.

[0017]

In order to solve the above-mentioned problems, the present invention provides a fuel cell comprising a fuel gas and an oxidizing gas obtained by steam reforming a hydrocarbon-based raw fuel,
In a fuel cell power generator that generates electric power based on an electrochemical reaction, the reformer for steam reforming, a CO shift converter and a CO remover for reducing the CO concentration in the reformed gas, A steam generator for generating steam for reforming by the sensible heat of the combustion exhaust gas of the reformer, and the feed water is passed in series to the CO converter, the CO remover, and the steam generator in order. A reforming steam supply line that mixes steam derived from the steam generator with the raw fuel and flows to the reformer; a steam outlet of the steam generator in the reforming steam supply line; A feedwater inlet for a reformer, which is connected to a feedwater inlet for the fuel cell power generator, to recirculate feedwater from the steam generator outlet to the CO converter and the CO remover when starting the fuel cell power generator; Line and said break And that a switching control valve for switching the flow of supply water to either use feed water recirculation line and reforming steam supply line (first aspect of the present invention).

According to the above configuration, when the fuel cell power generator is started, the supply water is returned from the steam generator outlet to the CO converter and the CO remover, so that the sensible heat of the combustion exhaust gas is used as the supply water as a medium. It can be used for raising the temperature of the CO converter and the CO remover. As a result, the electric heater for starting the CO converter and the CO remover becomes unnecessary.

Further, in the fuel cell power generator according to claim 1, a raw fuel supply line for mixing a part of the raw fuel with the combustion exhaust gas of the reformer and supplying it to a steam generator, An on-off valve provided on a fuel supply line, and the steam generator has a combustion catalyst therein for burning raw fuel with residual oxygen in the combustion exhaust gas. Invention).

As described above, the temperature of the reflux feed water at the time of startup is increased by installing the combustion catalyst in the flue gas flow passage of the steam generator and catalytically combusting the residual oxygen and the raw fuel in the flue gas. CO converter and C
The starting time of the O remover can be shortened.

As a method for starting the fuel cell power generator according to claim 1 or 2, the invention described in claim 3 or 4 is preferable. That is, the method for starting a fuel cell power generator according to claim 1, wherein when the fuel cell power generator is started, the combustion exhaust gas of the reformer is heated by the combustion exhaust gas while being supplied to a steam generator. The feed water is passed through a reforming feed water recirculation line to raise the temperature of the CO converter and the CO remover,
After the remover reaches a predetermined temperature, the flow of the supply water is switched to the reforming steam supply line (the invention of claim 3).

The method of starting a fuel cell power generator according to claim 2, wherein at the time of starting the fuel cell power generator,
In a state where the combustion exhaust gas of the reformer is supplied to a steam generator, the feed water heated by the combustion exhaust gas is passed through a reforming feed water recirculation line, and the CO converter and the CO remover are removed. After the temperature is raised and the CO converter and the CO remover reach a predetermined temperature, the flow of the supply water is switched to the reforming steam supply line, and the on-off valve of the raw fuel supply line is closed. As a result, the refueling of the steam generator is stopped (the invention of claim 4).

Further, in order to prevent the temperature rise of the CO converter and the CO remover, the invention of the following claim 5 is preferable.
That is, in the control method of the fuel cell power generator according to claim 3 or 4, wherein the reforming feedwater recirculation line individually bypasses the CO shift converter and the CO remover, and each bypass line. To the CO converter and the CO remover when the reactor reaches a predetermined temperature.
In order to prevent the temperature of the O remover from rising excessively, the reactor that has reached the predetermined temperature is switched to a bypass line so that the supply water flows.

[0024]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a system diagram showing an embodiment according to the present invention. Members having the same functions as those in FIG. The difference between FIG. 1 and FIG.
Generally, in FIG. 1, the part number 1
To 8 piping systems and members.

That is, first, in order to circulate the supply water at the time of starting, the reforming supply water recirculation line 1 returning from the steam generator 14 outlet to the pump inlet, the case where the cooling water is circulated, and the case where the reforming steam is used A shutoff valve 2 and a shutoff valve 3 are added as switching control valves for switching between supply and supply. At the time of startup, the flue gas combusted by the burner of the reformer 11 is deprived of sensible heat by exchanging heat with the supply water in the steam generator 14 and then exhausted.

At this time, the supply water can be circulated by closing the shut-off valve 3 and opening the shut-off valve 2, and the supply water is heated inside the steam generator 14, and then is supplied to the CO converter. 1
2 and the CO remover 13 by applying heat to the steam generator 14
Come back to. With this method, the sensible heat of the combustion exhaust gas from the reformer is used to convert the steam generator 14, the CO converter 12, the CO remover 1
3 can be heated, and the sensible heat of the combustion exhaust gas is more effectively used than ever.

On the other hand, during normal operation, on the other hand, the shut-off valve 3 is opened and the shut-off valve 2 is closed, and
2. Using the reaction heat of the CO remover 13 and the sensible heat of the flue gas in the steam generator 14 to generate steam, the reformer 11
Can be supplied to Note that the shutoff valves 2 and 3 may be three-way control valves.

As a method of shortening the start-up time, a combustion catalyst 6 is installed inside the steam generator 14, and the raw fuel is mixed with the combustion exhaust gas and supplied through the raw fuel supply line 4 provided with the on-off valve 5. At this time, by using the oxygen in the high temperature combustion exhaust gas as an oxidizing agent, it is possible to easily burn the raw fuel which is difficult to burn at normal temperature. This heat of combustion is added to the reaction heat of the CO converter 12 and the CO remover 13 and the temperature rise of the steam generator 14, so that the startup time can be shortened.

Further, in order to prevent the temperature of the CO converter and the CO remover from excessively rising, the reforming feed water recirculation line 1
Has a bypass line for individually bypassing the CO converter and the CO remover, and switching valves 7 and 8 for each bypass line.
When any one of the reactors of the O remover 13 reaches a predetermined temperature, the CO shift converter 12 and the CO remover 13 can be switched to a bypass line to flow the supply water.

[0031]

As described above, according to the present invention, a fuel gas and an oxidizing gas obtained by steam reforming a hydrocarbon-based raw fuel are supplied to a fuel cell, and power is generated based on an electrochemical reaction. A reformer for steam reforming, a CO converter and a CO remover for reducing the CO concentration in the reformed gas, and the combustion exhaust gas of the reformer from the feed water. And a steam generator for generating reforming steam by the sensible heat of
A reforming steam supply line that sequentially flows in series to an O shift converter, a CO remover, and a steam generator, mixes steam derived from the steam generator with raw fuel, and flows to the reformer; The steam outlet of the steam generator in the steam supply line for quality is connected to the feed water inlet of the CO converter. When the fuel cell power generator is started, the feed water is supplied from the steam generator outlet to the CO converter. Feed water recirculation line for recirculating the feed water and the CO remover, and switching for switching the flow of feed water to any of the feed water recirculation line for reforming and the steam supply line for reforming A control valve, and a raw fuel supply line for mixing a part of the raw fuel with the combustion exhaust gas of the reformer and supplying it to the steam generator, and provided on the raw fuel supply line. With an on-off valve, and The steam generator is provided with a combustion catalyst for burning raw fuel with residual oxygen in the flue gas inside the steam generator, and when the fuel cell power generator is started, the flue gas of the reformer is converted to a steam generator. In this state, the feed water heated by the flue gas is passed through a reforming feed water recirculation line to raise the temperature of the CO converter and the CO remover.
After the O remover reaches a predetermined temperature, the flow of the supply water is switched to the reforming steam supply line, and the on-off valve of the raw fuel supply line is closed to close the raw fuel to the steam generator. By stopping the replenishment, the sensible heat of the flue gas can be used to raise the temperature of the CO converter and the CO remover using the supply water as a medium. By combusting and effectively utilizing this heat, the structure of the CO converter and the CO remover can be simplified, the power consumption at the time of starting the power generator, and the start-up time can be shortened.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of a fuel cell power generator and a starting method according to the present invention.

FIG. 2 is a system diagram showing an example of a conventional fuel cell power generator.

[Explanation of symbols]

1: feedwater recirculation line for reforming, 2, 3: shut-off valve, 4:
Raw fuel supply line, 5: open / close valve, 6: combustion catalyst, 7,
8: switching valve, 10: fuel cell, 11: reformer, 12: C
O-transformers 12, 13: CO remover, 14: steam generator, 15: steam supply line for reforming.

Claims (5)

[Claims] 1. A fuel cell power generator for supplying a fuel gas and an oxidizing gas obtained by steam reforming a hydrocarbon-based raw fuel to a fuel cell and generating electric power based on an electrochemical reaction. A reformer for reforming, a CO shift converter and a CO remover for reducing the CO concentration in the reformed gas, and a reforming steam is generated from feed water by sensible heat of the combustion exhaust gas of the reformer. A steam generator for causing the feed water to flow in series with the CO converter, the CO remover, and the steam generator in order, and mixing the steam derived from the steam generator with the raw fuel to convert the feed water. A reformer steam supply line flowing to the reformer, a steam outlet of the steam generator in the reformer steam supply line, and a feed water inlet of the CO converter. When the equipment is started, supply water is steamed. A reforming feedwater recirculation line for refluxing from the gas generator outlet to the CO shift converter and the CO remover; and a feedwater to one of the reforming feedwater recirculation line and the reforming steam supply line. And a switching control valve for switching the flow of the fuel cell. 2. The fuel cell power generator according to claim 1, wherein a part of the raw fuel is mixed with the combustion exhaust gas of the reformer and supplied to a steam generator, and the raw fuel supply line is provided. An on-off valve provided on the supply line, and
The fuel cell power generator according to claim 1, wherein the steam generator includes a combustion catalyst for burning a raw fuel with residual oxygen in the combustion exhaust gas. 3. The method for starting a fuel cell power generator according to claim 1, wherein the combustion exhaust gas from the reformer is supplied to a steam generator when the fuel cell power generator is started. The heated feed water is passed through a reforming feed water recirculation line, and the CO converter and CO
The temperature of the remover is raised, and after the CO shift converter and the CO remover reach a predetermined temperature, the flow of the supply water is switched to the reforming steam supply line. starting method. 4. The method for starting a fuel cell power generator according to claim 2, wherein at the time of starting the fuel cell power generator, the combustion exhaust gas from the reformer is supplied to a steam generator. The heated feed water is passed through a reforming feed water recirculation line, and the CO converter and CO
After the temperature of the remover is raised and the CO shift converter and the CO remover reach a predetermined temperature, the flow of the supply water is switched to the reforming steam supply line, and the opening and closing of the raw fuel supply line is further performed. A method for starting a fuel cell power generator, comprising closing a valve to stop supplying raw fuel to a steam generator. 5. The method for starting a fuel cell power generator according to claim 3 or 4, wherein the reforming feedwater recirculation line bypasses the CO converter and the CO remover individually, A switching valve to each bypass line, and when either the CO converter or the CO remover reaches a predetermined temperature, in order to prevent the CO converter and the CO remover from overheating, A method for starting a fuel cell power generator, characterized in that the reactor that has reached the predetermined temperature is switched to a bypass line so that the supply water flows.