JP2002050386A - Hydrogen producing device for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply the amount of heat required for reforming reaction of raw material gas not only by the combustion of the fuel cell exhaust gas but also by the combustion of part of the fuel gas. SOLUTION: The exhaust gas discharged from the fuel cell 20 is burned by a burner 3 by being mixed with the air, and by this heat energy the combustion catalyst 1 and the reforming catalyst 2 are heated. At this point, part of the raw material gas that is introduced from a piping 10 is partially burnt and part of the fuel gas is oxidized in the combustion catalyst 1. When methane is used as the raw material gas, hydrogen and water vapor or the like are generated by the reaction of methane and oxygen. When the remaining raw material gas and water vapor are reacted by the reforming catalyst 2, hydrogen is generated by reforming reaction and hydrogen-rich reforming gas 14 is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen production apparatus for a fuel cell, and more particularly to a fuel suitable for producing hydrogen from a raw material gas containing hydrocarbons such as natural gas by utilizing exhaust gas from a fuel cell. The present invention relates to an apparatus for producing hydrogen for a battery.

[0002]

2. Description of the Related Art Since a polymer electrolyte fuel cell operates at a low temperature, it is expected to be put to practical use as a drive power supply for automobiles or a distributed power supply. This polymer electrolyte fuel cell has a cell in which an anode and a cathode are arranged via an electrolyte layer,
A plurality of separator plates that supply hydrogen-rich gas to the anode and oxidant gas such as air to the cathode are stacked alternately and assembled, and the electrochemical reaction between hydrogen in the anode gas and oxygen in the cathode gas is performed. Then, the chemical energy generated at that time is taken out as electric energy.

In this type of fuel cell, a light hydrocarbon such as natural gas (methane gas) or naphtha is used as a fuel serving as a hydrogen source, and a fuel gas containing such a light hydrocarbon is hydrogen-rich. A fuel gas reformer for steam reforming the anode gas (reformed gas) is provided separately from the fuel cell.

[0004] As a fuel gas reforming apparatus, for example, there is one described in JP-A-9-153372. As shown in FIG. 4, the fuel gas reformer mixes steam and a raw material (natural gas) with an ejector 31, preheats the mixed gas in a heat exchanger 32, and reforms the preheated gas. The reformer 30 introduces the fuel cell 2
The mixed gas is steam-reformed into a hydrogen-rich anode gas (reformed gas) by burning the fuel gas exhaust gas discharged from the fuel cell 20 through the heat exchanger 32.
To the anode. That is, in the reformer, basically, the unreacted exhaust gas of the fuel cell 20 is burned in the reformer 30 so that the heat of the endothermic reaction required for the reforming reaction can be generated. I have.

[0005]

However, in the prior art, when the hydrogen utilization rate in the fuel cell 20 is high, the amount of heat required for the reforming reaction in the reformer 30 is insufficient. If fuel gas such as natural gas is used to compensate for this, the thermal efficiency will decrease. That is, in the prior art, the amount of heat required for the reforming reaction in the reformer 30 cannot always be supplied, and when this shortage of heat is replenished by burning natural gas or the like, the heat efficiency decreases. There is a problem that invites.

SUMMARY OF THE INVENTION An object of the present invention is to supply not only the heat required for the reforming reaction of the raw material gas by burning the exhaust gas from the fuel cell but also to make up for the fuel by burning part of the fuel gas. An object of the present invention is to provide a hydrogen production device for a battery.

[0007]

In order to achieve the above object, the present invention provides a combustion furnace for burning residual hydrogen in exhaust gas discharged from a fuel cell, and a method for receiving a raw material gas containing hydrocarbons. A combustion catalyst for burning part of the gas,
The combustion furnace receives heat energy from combustion from the combustion catalyst and reacts the steam generated with the combustion of the source gas with the remaining source gas of the source gas to produce a hydrogen-rich reformed gas. This constitutes a hydrogen production apparatus for a fuel cell including a reforming catalyst to be generated.

The following elements can be added when configuring the hydrogen production apparatus for a fuel cell.

(1) The combustion furnace is housed in a central portion of a cylindrical container, and the combustion catalyst and the reforming catalyst are arranged on the outer peripheral side of the combustion furnace and housed in the cylindrical container. .

(2) In the cylindrical container, C for removing carbon monoxide from the reformed gas generated by the reforming catalyst is provided.
The O converter is housed.

According to the above-described means, the amount of heat required for reforming the source gas includes the heat energy generated by burning the hydrogen remaining in the exhaust gas of the fuel cell and the heat energy generated by burning a part of the source gas. The energy is compensated by the energy, and even when the hydrogen utilization rate in the fuel cell is high, the calorie required for the reforming reaction can be supplemented. Can be supplied to

Here, for example, when methane is used as a raw material gas and a part of the methane is burned at a stoichiometric ratio or less, the fuel gas undergoes the following reaction.

CH ₄ + 1 / 2O ₂ = 2H ₂ + CO (1) CH ₄ + 2O ₂ = CO ₂ + 2H ₂ O (2) The reaction at this time is an exothermic reaction and is necessary for a fuel cell. There is an advantage that generated hydrogen is generated.

In the process in which part of the raw material gas is partially burned by the combustion catalyst to generate hydrogen by the reactions of the formulas (1) and (2), the steam generated by the reaction of the formula (2) It reacts with the gas and generates hydrogen by the reforming reaction of the following formula.

CH ₄ + H ₂ O = 3H ₂ + CO (3) That is, when the steam reacts with the remaining source gas in the reforming catalyst, a hydrogen-rich reformed gas is generated.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a hydrogen production apparatus for a fuel cell according to the present invention, FIG. 2 is a sectional view taken along line AA ′ of FIG. 1, and FIG. 3 is a block diagram of a fuel cell system including the hydrogen production apparatus for a fuel cell. It is a block diagram.

In FIGS. 1 and 2, the hydrogen production apparatus for a fuel cell is configured as a cylindrical container as a whole.
A combustion furnace 23 formed in a cylindrical shape is housed in the center thereof. The outer peripheral side of the combustion furnace 23 is covered with an inner cylinder and an outer cylinder, and the heat insulating material 9 is stored between the inner cylinder and the outer cylinder. The burner 3 is arranged on the bottom side of the combustion furnace 23, and the battery exhaust gas / air supply pipe 11 is connected to the burner 3. The evaporator 4 is accommodated in the combustion furnace 23, and a combustion exhaust gas outlet pipe 12 is connected to an upper side of the combustion furnace 23.

Between the combustion furnace 23 and the inner cylinder, a combustion catalyst 1, a reforming catalyst 2 are housed, and a steam heater 5, an air heater 6, and a raw material heater 7 are housed. .
Further, a reformed gas outlet pipe 13 is provided between the inner cylinder and the outer cylinder, and a CO converter 8 is provided. A raw material gas such as a natural gas (methane gas) is supplied to the combustion catalyst 1 as a raw material from a raw material / air / vapor supply pipe 10, and air and vapor are supplied.

In the hydrogen production apparatus for a fuel cell having the above structure, the exhaust gas and the air discharged from the fuel cell 20 are introduced into the pipe 11, and the residual hydrogen and the air in the exhaust gas are mixed and burned by the burner 3. The combustion catalyst 1 and the reforming catalyst 2 are heated by the heat energy of the combustion gas generated at this time. After the combustion gas is recovered in the evaporator 4, the combustion gas is discharged out of the system through the combustion exhaust gas outlet pipe 12.

On the other hand, a raw material (raw material gas), air and steam are supplied to the combustion catalyst 1 from a pipe 10, and a part of the raw material gas is partially burned in the combustion catalyst 1 to form a part of the fuel gas. Is oxidized. When methane is used as this source gas, hydrogen is generated by the reactions of the above formulas (1) and (2). Further, the remaining raw material gas of the raw material gas and the steam generated by the reaction of the formula (2)
, Hydrogen is generated by the reforming reaction of the formula (3).

The reaction in equation (3) is an endothermic reaction,
The amount of heat required for the endothermic reaction is supplied by thermal energy (sensible heat) generated when a part of the fuel gas is partially burned by the combustion catalyst 1 and thermal energy generated by burning the burner 3.

The reforming catalyst 2 generates a hydrogen-rich reformed gas, and the temperature of the generated reformed gas is 70%.
About 0 ° C., and the reformed gas 14
After the heat is recovered by the air heater 6 and the raw material heater 7, the flow direction is reversed and introduced into the CO converter 8.

In the CO converter 8, carbon monoxide is removed from the reformed gas by the following reaction.

CO + H ₂ O = H ₂ + CO ₂ (4) The reformed gas from which CO (carbon monoxide) has been removed by the CO converter 8 is supplied to a CO selective oxidizer (not shown), After the remaining CO is oxidized and removed by air, it is supplied to the anode of the fuel cell 20.

When the reformed gas is supplied to the anode of the fuel cell 20, hydrogen in the reformed gas and an oxidizing agent such as oxygen in the cathode gas undergo an electrochemical reaction, and the chemical energy generated at that time is reduced. It is converted into electrical energy to generate electric power.

In this case, as shown in FIG.
The steam, air and raw material (raw material gas) heated by the reformed gas 25 are supplied from the steam heater 5, the air heater 6, and the raw material heater 7 to the , The steam, the air, and the raw material (raw material gas) can be heated using the sensible heat of the reformed gas 20. Further, cooling water for cooling the fuel cell 20 is supplied to the evaporator 4, and the steam generated from the evaporator 4 by the combustion exhaust gas generated from the combustion furnace 23 is separated into steam and drain by the steam separator 21. The separated steam is supplied to the steam heater 5. In addition,
A part of the heat generated in the combustion furnace 23 is supplied to the reforming section 22.

As described above, in the present embodiment, during the steady operation, the steam generated along with the combustion of the raw material gas is reacted with the remaining raw material gas to form a hydrogen-rich reformed gas. In the combustion furnace 23, the heat energy required for generating the fuel gas is obtained by burning the thermal energy (thermal energy associated with partial oxidation) associated with the combustion of the raw material gas in the combustion catalyst 1 and the hydrogen remaining in the exhaust gas generated from the fuel cell 20. Since it is made up for by the heat energy generated at the time, it is possible to use only the former energy or the combustion furnace 23.
The thermal efficiency can be improved as compared with the case where the fuel other than the remaining hydrogen is supplied and burned.

At the time of startup, sufficient heat energy is not obtained by partial combustion of the fuel gas in the combustion catalyst 1 and no hydrogen is generated, so that heat generated by the combustion of hydrogen remaining in the exhaust gas discharged from the fuel cell is not obtained. When the generation of fuel cannot be expected or when the amount of residual hydrogen in the fuel cell exhaust gas is small, the temperature of the reforming unit 22 can be increased by supplying another fuel to the combustion furnace 23 and burning it. .

Specifically, at the time of startup, generating steam for reforming the source gas (methane) is the key to shortening the startup time. That is, the steam is usually supplied as superheated steam, and the temperature of the superheated steam is increased by the heat absorbed by the evaporator 4 and the steam heater 5. Since the heat absorption of the evaporator 4 with latent heat accounts for the majority of the heat absorption, in order to raise the temperature of normal-temperature water to a predetermined superheated steam, methane or the like is supplied to the combustion furnace 23 as a raw material gas. By increasing the amount of heat absorbed by the evaporator 4, the necessary superheated steam conditions can be achieved quickly.

Therefore, the start-up time can be reduced by installing the combustion furnace 23 inside the apparatus.

Further, the amount of heat absorbed necessary for the reforming reaction is determined by comparing the thermal energy (external heat) from the combustion gas with the raw material gas (methane).
Can be supplied from the heat energy (internal heat) generated by the combustion of the fuel cell. Therefore, even if the reformer, that is, the container storing the combustion catalyst 1 and the reforming catalyst 2 is made compact, a predetermined amount of hydrogen can be secured.

In the combustor 23, the evaporator 4 is desirably installed above the combustion furnace 23 in order to secure the amount of electric heat to the combustion catalyst 1 and the reforming catalyst 2 by the combustion gas of the burner 3. .

The combustion gas cooled by the evaporator 4 is supplied to a steam superheater 5 and an air superheater
Further, since the amount of heat transfer can be ensured also for the raw material superheater 7, the temperature of the combustion exhaust gas can be reduced, and the heat loss of the exhaust gas can be reduced.

Therefore, according to the present embodiment, the following effects can be obtained.

(1) The amount of heat required for the reforming reaction can be supplemented by partial oxidation and external heat, the required amount of hydrogen can be secured, the amount of heat of the combustion gas can be effectively used, and the heat efficiency can be improved. It can contribute to improvement.

(2) The fuel required for the reforming reaction is supplemented not only by the thermal energy associated with the combustion of the exhaust gas of the fuel cell but also by the thermal energy associated with the partial fuel of the raw material gas. Even if it fluctuates, a hydrogen-rich reformed gas can be supplied to the fuel cell.

(3) The heat loss of the combustion furnace 23 can be reduced as compared with the case where the combustion furnace 23 for burning the fuel cell exhaust gas is separately provided.

(4) Since the portion where the gas temperature is low is arranged on the outer peripheral side of the combustion furnace 23, heat loss through the heat insulating material 9 can be reduced.

(5) At the time of startup when the fuel cell 20 does not take a load, since the calorie of the exhaust gas of the fuel cell is high, the combustion catalyst 1 and the exhaust catalyst 2 can be heated by the combustion heat, and the startup time is reduced. Can be shortened.

[0040]

As described above, according to the present invention,
The amount of heat required for reforming the raw material gas is supplemented by the thermal energy generated by burning the hydrogen remaining in the exhaust gas of the fuel cell and the thermal energy generated by burning part of the raw material gas. Even when the utilization rate is high, the amount of heat required for the reforming reaction can be supplemented, and the hydrogen-rich reformed gas can be supplied to the fuel cell even if the calories of the exhaust gas of the fuel cell fluctuate.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a fuel cell hydrogen production apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the device shown in FIG. 1, taken along line AA ′.

FIG. 3 is a block diagram of a fuel cell system according to the present invention.

FIG. 4 is a block diagram of a conventional fuel cell system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion catalyst 2 Reforming catalyst 3 Burner 4 Evaporator 5 Steam heater 6 Air heater 7 Raw material heater 8 CO converter 9 Insulation material 10 Raw material / air / steam supply pipe 11 Battery exhaust gas / air supply pipe 12 Combustion exhaust gas outlet pipe 13 Reformed gas outlet pipe 14 Reformed gas 20 Fuel cell 23 Combustion furnace

Claims (3)

[Claims] 1. A combustion furnace for burning hydrogen remaining in exhaust gas discharged from a fuel cell, a combustion catalyst for receiving a raw material gas containing hydrocarbons and burning a part of the raw material gas,
The combustion furnace receives heat energy from combustion from the combustion catalyst and reacts the steam generated with the combustion of the source gas with the remaining source gas of the source gas to produce a hydrogen-rich reformed gas. A hydrogen production apparatus for a fuel cell, comprising a reforming catalyst to be generated. 2. The combustion furnace is housed in a central portion of a cylindrical vessel, and the combustion catalyst and the reforming catalyst are arranged on an outer peripheral side of the combustion furnace and housed in the cylindrical vessel. Item 2. A hydrogen production apparatus for a fuel cell according to item 1. 3. The hydrogen production apparatus for a fuel cell according to claim 2, wherein a CO converter for removing carbon monoxide from the reformed gas generated by the reforming catalyst is accommodated in the cylindrical container. .