JP2003040602A - Apparatus for producing hydrogen for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply hydrogen produced by decomposition of hydrogen resources such as ammonia, and to utilize an exhaust gas from a fuel cell for preventing hazardous substance releasing by. SOLUTION: An hydrogen producing apparatus is composed of a decomposer 2 in which the hydrogen resources are decomposed to nitrogen and hydrogen and to supply them to the fuel cell, a combustor 3 to combust the exhaust gas from the fuel cell 4 by a catalytic reaction, air feeding means 5 to feed combustion air to the combustor 3, an oxygen sensor 34 to measure oxygen concentration in the exhaust gas from the combustor 3 and a controller 6 to control the air feeding means 5. As the hazardous substance such as ammonia in the exhaust gas from the fuel cell is combusted and removed in the combustor 3, the releasing of the hazardous substances can be prevented. When heat from the combustor 3 is fed to the decomposer 2, energy efficiency is improved because a heat source to heat the decomposer 2 is not required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing hydrogen supplied to a fuel cell, and more particularly to an optimal hydrogen producing apparatus for a fuel cell vehicle.

[0002]

2. Description of the Related Art In recent years, automobiles driven by fuel cells using hydrogen as fuel have been actively developed. Exhaust gas from a fuel cell that uses hydrogen as a fuel does not contain harmful substances or carbon dioxide unlike exhaust gas from an internal combustion engine, and therefore the fuel cell is most suitable as clean energy capable of suppressing environmental pollution and global warming.

However, in a fuel cell for an automobile, a means for supplying hydrogen, which is a fuel, has been a problem. For example, in order to supply the hydrogen gas itself, it is necessary to compress or liquefy the hydrogen and install it. However, when hydrogen is filled at a pressure of 200 atm in a pressure vessel with an internal volume of 50 L, which corresponds to the internal volume of the current gasoline tank. The amount is only 0.4kg, the internal volume is 50L
Even if the adiabatic pressure vessel is filled with liquefied hydrogen, the amount of hydrogen is 3.5 kg. Therefore, in the case of long-distance travel, hydrogen must be replenished frequently, and the maintenance of infrastructure such as hydrogen stations becomes an issue.

A method of decomposing cyclohexane to produce hydrogen is also known. By decomposing 1 mol of cyclohexane, 3 mol of H ₂ is produced, and 2.8 kg of H ₂ is produced from liquid cyclohexane filled in a container having an internal volume of 50 L.
Further, cyclohexane is a liquid at room temperature, so that it can be easily mounted on an automobile.

However, in the decomposition reaction of cyclohexane, there is a problem that harmful benzene is produced as a by-product, and since the boiling points of cyclohexane and benzene are close to each other, it is difficult to separate the two from the decomposition gas. is there.

Further, the method using a hydrogen storage alloy can store only 1.5 to 2% of hydrogen per unit weight of the alloy, and hydrogen can be produced even when sodium borohydride or sodium metal is reacted with water. There is a problem that recycling of living things is difficult.

Therefore, a method of decomposing ammonia to produce hydrogen is drawing attention. The decomposition of 1 mol of ammonia produces 1.5 mol of H ₂ . Further, since ammonia can be stored in a liquefied state at room temperature, there is an advantage that an adiabatic pressure vessel is not required. And the internal volume
7.2 from liquefied ammonia filled in a 50 L pressure vessel
It is a promising hydrogen source because it can produce kg H ₂ and produces the most H ₂ by volume and by weight.

For example, in JP-A-54-126689, ammonia is decomposed into N ₂ and H ₂ at 900 to 950 ° C. using a Ni-based catalyst, and a small amount of residual ammonia and water is stored in a synthetic zeolite at room temperature. Absorbing is disclosed. Also pure
To obtain H _2, it is also disclosed that the separation between N2 and liquefied.

Alternatively, Japanese Patent Laid-Open No. 7-331265 discloses that ammonia and an ammonia decomposition product (H ₂ ) are used as fuel for an internal combustion engine.
Is used.

[0010]

However, since the decomposition reaction of ammonia is an equilibrium reaction, the produced gas contains ammonia. Therefore, when used as a hydrogen source for a fuel cell vehicle, ammonia is contained in the exhaust gas from the fuel cell, which is not preferable.

The present invention has been made in view of such circumstances, and by supplying hydrogen produced by decomposing a hydrogen source such as ammonia to a fuel cell and further utilizing exhaust gas from the fuel cell. The purpose is to prevent the emission of harmful substances.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The feature of the hydrogen producing apparatus for a fuel cell of the present invention which solves the above-mentioned problems is that a hydrogen source comprising at least one of ammonia and hydrazine is decomposed into nitrogen and hydrogen by a catalytic reaction to produce a fuel cell. Decomposing unit for supplying, combustor for burning exhaust gas from fuel cell by catalytic reaction, air supply means for supplying combustion air to the combustor, and oxygen concentration detection for detecting oxygen concentration in exhaust gas from the combustor And a control device for controlling the air supply means according to at least the oxygen concentration value detected by the oxygen concentration detector.

The combustor preferably supplies the combustion heat of the exhaust gas to the decomposer. Further, it is desirable that the fuel cell be operated at a temperature of 100 ° C. or higher.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the hydrogen production apparatus of the present invention, the exhaust gas from the fuel cell is combusted in the combustor. Therefore, harmful substances such as ammonia contained in the exhaust gas from the fuel cell are burned and removed by the combustor, so that the emission of the harmful substances can be prevented. And since the hydrogen source can be stored in a liquefied state at room temperature, it can be installed in an automobile without the need for an adiabatic pressure vessel, and since the amount of hydrogen produced per mole of hydrogen source is large, it can be run for a long distance with one filling. Is possible.

Further, it is desirable that the combustor supplies combustion heat generated by burning exhaust gas from the fuel cell to the decomposer. As a result, the emission of harmful substances can be prevented, and a heat source for heating the decomposer is not required, thus improving energy efficiency.

The constituent elements will be described below in order.

At least one of ammonia and hydrazine is used as the hydrogen source. Hydrazine (N ₂ H ₄ )
In the decomposition of (1), 1 mol of hydrazine produces 2 mol of H _2, but since it is a liquid at room temperature, there is an advantage that a pressure resistant container is unnecessary. The amount of H ₂ produced from hydrazine filled in a container with an internal volume of 50 L is about 6.3 kg, which is slightly less than that in the case of liquefied ammonia, but when the container is included, it is much higher in weight efficiency and volume efficiency than other hydrogen sources. In the following description, the case where ammonia is used as the hydrogen source will be described.

Ammonia liquefies relatively easily by compression, for example, at 30 ° C., it liquefies at 11.5 atm. Therefore, it can be stored in a simple pressure-resistant container such as an LPG cylinder. Further, for example, the safety can be improved by filling the container with an ammonia absorbent such as zeolite. However, in this case, a device for taking out ammonia such as a heating device or a pump is required.
Further, when the size (storage space) of the storage container has a margin, it is possible to store the ammonia water at a low pressure in a safe handling form. Coexistence of water causes almost no disadvantage when supplying the fuel cell.

The decomposer produces ammonia by the reaction of the following equation.
It is decomposed into N ₂ and H ₂ and supplied to the fuel cell.

2NH ₃ → N ₂ + 3H ₂ This decomposition reaction is an equilibrium reaction, and progresses toward the right side as the pressure becomes lower and the temperature becomes higher.

By the way, in recent years, a method of reforming methanol to produce hydrogen has been proposed. This reaction formula is shown below.

CH ₃ OH + H ₂ O → CO ₂ + 3H ₂ This methanol reforming reaction requires 32 g of methanol and 18 g of water to produce 3 mol of H ₂ , and its volume is 40.5 ml of methanol. With 18 ml of water, the total amount becomes 58.5 ml, but in the above ammonia decomposition reaction, 34 g of ammonia is sufficient for producing 3 mol of H ₂ , and the volume thereof becomes 57 ml. Therefore, the ammonia decomposition reaction is more advantageous than the methanol reforming reaction because it requires a smaller container volume. Further, in the methanol reforming reaction, carbon monoxide, which significantly deteriorates the performance of the fuel cell, and an adverse effect on the human body and generation of elementary formaldehyde may occur.

The decomposition reaction of ammonia occurs at 1000 ° C. or higher, preferably 1200 ° C. or higher when no catalyst is used, but in consideration of mounting on an automobile, it is necessary to lower the temperature by utilizing the catalyst. Therefore, in the present invention, the ammonia decomposition reaction is performed by the catalytic reaction in the decomposer.

As the ammonia decomposition catalyst, Ni, Co, Fe are used.
Catalysts containing a transition metal such as or the like or an oxide thereof as a main component have been known for a long time, and it is also possible to use these catalysts in the decomposer of the present invention. However, these catalysts are usually designed for continuous operation, and stable performance is not exhibited in the case of ammonia decomposition reaction for fuel cell vehicles in which the reaction is repeatedly started or stopped. It will be difficult. Therefore, in the case of the present invention,
Noble metal catalysts such as Pt, Rh, Pd, Ru are preferred, and Rh,
It is desirable to use one or more of Ru and Pt. It is also preferable to use a noble metal catalyst and the above transition metal-based catalyst in combination.

The decomposer is preferably constructed so that the contact area between ammonia and the catalyst becomes large. Therefore, for example, it is preferable to have a structure in which a pellet catalyst in which a catalyst component is supported on a pellet-shaped porous base material is filled in a cylinder, or a structure in which the catalyst is supported on a honeycomb-shaped or foam-shaped base material. More preferably, a decomposer having a material and a shape having good thermal conductivity is required so as to efficiently take in heat from the outside.

The amount of the catalytic metal supported on the substrate is
The range of 0.02 to 5% by weight is preferable. If it is less than this range, the catalyst volume for obtaining the necessary reaction becomes too large, which is not practical. Further, even if the catalyst is further supported, the reaction is an endothermic reaction, so that the heat cannot be supplied in time, the temperature of the catalyst is lowered, and the performance as much as the amount of the supported catalyst cannot be exhibited. Then, N ₂ and H ₂ generated by the decomposer and a small amount of ammonia that is not decomposed are supplied to the fuel cell.

When a noble metal catalyst is used, the ammonia decomposition reaction occurs at 400 ° C. or higher. The ammonia decomposition reaction is an endothermic reaction. Therefore, in order to efficiently carry out the ammonia decomposition reaction in the decomposer, it is necessary to supply heat in addition to supporting the catalyst. As this heat source, an external heater can be used, or air can be introduced into the decomposer to oxidize a part of ammonia to use its combustion heat. However, as described later, the combustion heat of the combustor can be used. desirable.

There is no restriction on the fuel cell to which the hydrogen production apparatus of the present invention is applied, but in a fuel cell using a proton conductor using a solid polymer membrane, ammonia is generated when it is operated at a temperature lower than 100 ° C. It may be strongly adsorbed on the fuel electrode and the polymer membrane to hinder the electric output. However, if the fuel cell is operated at 100 ° C. or higher, the adsorption of ammonia is reduced, so that such a problem is greatly reduced, and the fuel cell can be used for automobiles without trouble. The limitation of 100 ° C. or higher is applied when hydrogen containing 100 ppm or less of ammonia is supplied to the fuel cell at normal pressure. When starting the hydrogen production device, or when supplying to the fuel cell by pressurizing it to 1 atm or more, when a large amount of ammonia is momentarily generated, it is directly supplied to the combustor without passing through the fuel cell. It is necessary to select a fuel cell that operates at a higher temperature or install an ammonia adsorption device between the decomposer and the fuel cell. These ideas are within the scope of the prior art and will not be described in detail.

However, since the ammonia in the decomposition gas supplied to the fuel cell is discharged from the fuel cell as it is, there is a problem that the exhaust gas of the fuel cell vehicle contains ammonia. Therefore, in the present invention, the exhaust gas from the fuel cell is burned by a catalytic reaction using a combustor.

In the exhaust gas from the fuel cell, N ₂ and a small amount of ammonia produced by the decomposition of ammonia and H ₂ which could not be consumed are present. When combusting ammonia, if oxygen is insufficient, unburned ammonia will be discharged. Therefore, in the present invention, a catalyst is also used in the combustor to completely burn ammonia and H ₂ .

As this catalyst, it is preferable to use an oxidation catalyst, a three-way catalyst or the like which is used as an exhaust gas purifying catalyst for automobiles. That is, it is desirable to use a catalyst in which at least one selected from Pt, Rh, and Pd is supported on a heat-resistant porous oxide carrier such as alumina or zirconia. Then, as the combustor, similar to the decomposer, a structure in which a pellet catalyst supporting a precious metal on a pellet-shaped base material is filled in a cylinder, a structure in which a precious metal is supported on a honeycomb-shaped or foam-shaped heat-resistant base material, and the like. Preferably.

The amount of the noble metal supported on the substrate was 0.
The range of 02 to 10% by weight is preferable. If the amount is less than this range, the effect of loading will not be exhibited, and if it is loaded more than this range, the effect will be saturated and the cost will increase.

By using such a combustor, ammonia and H _{2 in} the exhaust gas from the fuel cell are easily combusted in the presence of a catalyst in the combustor due to the coexistence of oxygen,
It is emitted as harmless N ₂ and H ₂ O.

However, in the combustor, unburned ammonia and hydrogen are discharged when oxygen is insufficient, and nitrogen oxides are generated when oxygen is excessive, which is not preferable. Therefore, in the present invention, an air supply means for supplying combustion air to the combustor, an oxygen concentration detector for detecting the oxygen concentration in the exhaust gas from the combustor, and at least the oxygen concentration value detected by the oxygen concentration detector. A control device that controls the air supply means accordingly is a constituent feature.

That is, when the oxygen concentration value detected by the oxygen concentration detector is larger than the predetermined value, oxygen is excessive, so the air supply means is controlled to reduce the oxygen supply amount,
When the detected oxygen concentration value is smaller than the predetermined value, the oxygen is insufficient, so the air supply means is controlled to increase the supply oxygen amount. By performing such feedback control, ammonia and hydrogen contained in the exhaust gas from the fuel cell can be completely combusted, and the production of nitrogen oxides can be prevented.

The air supply means is not particularly limited as long as it can supply combustion air to the combustor, and a flow path having one end communicating with the combustor and the other end communicating with the atmosphere, and a valve for opening and closing the flow path. , A pump, etc. can be adopted. Further, an oxygen sensor or the like can be used as the oxygen concentration detector, and the control means can be composed of a digital circuit or the like using a microcomputer. The combustion air may be the atmosphere or gas discharged from the air electrode of the fuel cell.

The combustor is preferably constructed so that the combustion heat of exhaust gas can be supplied to the decomposer. As a result, a heat source such as a heater for heating the decomposer can be eliminated, and a more compact device can be obtained. It is also possible to supply air to the decomposer and burn part of the ammonia to utilize the heat. In this case, the produced hydrogen is diluted with nitrogen in the introduced air to reduce the concentration, but if the heat of the combustor is used as described above, such a problem does not occur.

In order to supply the heat of the combustor to the decomposer, known heat exchange methods such as a method of arranging the combustor on the outer or inner circumference of the decomposer, a method of overlapping or intersecting the gas flow paths of each other, etc. A configuration similar to that of the container can be adopted.

By the way, if only the exhaust gas from the fuel cell is used,
For example, at the time of starting or when the output of the fuel cell suddenly changes from low to high, the amount of heat generated in the combustor may be insufficient for the decomposition reaction in the decomposer. In such a case, a part of ammonia, which is a fuel, can be supplied to the combustor for combustion. Even in this case, it is possible to supply the optimum amount of air by controlling the air supply means and prevent the generation of nitrogen oxides.

Although it is desirable that the exhaust gas from the fuel cell be burned in the combustor in its entirety, it can be discharged as it is when the operation of the automobile is stopped. However, since it is not preferable to discharge ammonia, in such a case, it is desirable to discharge it through the ammonia remover. As such an ammonia remover, for example, a catalyst in which zeolite carries Cu, Pt, or the like can be used. By using such a catalyst, it is possible to purify efficiently N ₂ and H ₂ O ammonia in 100 ° C. or more exhaust gas discharged from the fuel cell with oxygen excess conditions, H ₂ is H
Can be purified to ₂ O.

The output of the fuel cell is proportional to the amount of hydrogen supplied, and the amount of hydrogen corresponds to the amount of ammonia supplied to the cracker. Therefore, when supplying hydrogen produced by the hydrogen production apparatus of the present invention to a fuel cell vehicle, it is desirable to control the ammonia supply amount according to the operating conditions of the vehicle. That is, when the fuel cell requires high output, the ammonia supply amount is increased, and when not, the ammonia supply amount is decreased. The required output of the fuel cell may be calculated, for example, by inputting an electric signal corresponding to the state of the accelerator of the automobile into the control device and performing the arithmetic operation in the control device.

[0042]

EXAMPLES The present invention will be specifically described below with reference to examples. The hydrogen production apparatus of this embodiment is mounted on a fuel cell vehicle and used to supply hydrogen to the fuel cell.

(Embodiment 1) FIG. 1 shows a block diagram of a hydrogen producing apparatus for a fuel cell of this embodiment. This hydrogen production apparatus includes an ammonia cylinder 1, a cracker 2, a combustor 3,
The fuel cell 4 is mainly composed of a fuel cell 4, an air supply means 5, and a controller 6.

Liquefied ammonia is filled in the ammonia cylinder 1, and the ammonia is supplied to the decomposer 2 in a vaporized state via the feeder 10 and the valve 11. Then, the ammonia is decomposed by the decomposer ₂ , and a gas containing N ₂ , H ₂ and a trace amount of ammonia is supplied to the fuel cell 4. The feeder 10 is configured so that the controller 6 can control the amount of ammonia supplied to the cracker 2.

The exhaust gas of the fuel cell 4 is supplied to the combustor 3 via the valve 30. Air from the air supply means 5 is also supplied to the combustor 3. As a result, hydrogen and ammonia in the exhaust gas of the fuel cell 4 are burned in the combustor 3. Also valve 11 is a valve
A part of the ammonia vaporized from the feeder 10 is connected to the combustor 3 and can be supplied to the combustor 3.

The combustor 3 is formed integrally with the decomposer 2,
The combustion heat of the combustor 3 is transferred to the decomposer 2. FIG. 2 shows details of the decomposer 2 and the combustor 3.
The decomposer 2 has a plurality of decomposition channels 20, and the decomposition channel 20 is a porous carrier formed by sintering an alumina / zirconia mixture.
A pellet catalyst 21 containing 0.2 and 0.8 wt% of Ru and Pt, respectively, is filled. The respective decomposition flow paths 20 become one at the end, and the decomposition gas is supplied to the combustion cell 4 from the outlet 22. Further, the combustor 3 has a plurality of combustion flow passages 31, and Pt and Rh are loaded on the oxide porous support in which alumina and ceria are mixed at a ratio of 20: 1 in the combustion flow passages 31 at 0.8 and 0.2 wt% respectively. The resulting pellet catalyst 32 is filled. The ends of each combustion flow path 31 are connected to each other by a communication path (not shown) and are exhausted from the outlet 33.

The decomposition flow paths 20 and the combustion flow paths 31 are alternately formed adjacent to each other, and the heat generated by the combustion in the combustion flow paths 31 is transferred to the decomposition flow paths 20. An oxygen sensor 34 is arranged at the outlet 33 of the combustor 3 so that the oxygen concentration in the exhaust gas from the combustor 3 can be detected.

Exhaust gas (air with reduced oxygen concentration) and the atmosphere from the air electrode of the fuel cell 4 are supplied to the air supply means 5, and the combustor 3 is controlled by the control device 6.
The amount of air supplied to the system is controlled.

Exhaust gas from the fuel cell 4 passes through the valve 40 controlled by the control device 6 and the combustor 3 and the catalyst 41.
It is also supplied to one side and can be discharged to the outside via the catalyst 41. This catalyst 41 contains Pt of 0.1 in zeolite.
It is a catalyst that supports 4 wt% of Cu and 4 wt% of Cu, and can easily convert ammonia into nitrogen and water in an oxygen excess atmosphere at 100 ° C or higher.

The decomposer 2 and the combustor 3 are each provided with a temperature sensor (not shown), and the output signal thereof is input to the control device 6. Further, a Pt wire (not shown) is arranged in the exhaust gas passage of the fuel cell 4, and the hydrogen concentration in the exhaust gas can be measured by the thermal conductivity method.

The fuel cell 4 uses a proton conductor using a solid polymer membrane, and is constructed so as to operate at a temperature of 100 ° C. or higher.

The control device 6 is composed of a digital circuit mainly composed of a microcomputer, and receives the output from the temperature sensor and the Pt line, the supply device 10, the air supply means 5, the valve 11,
Controls 30 and 40.

The operation of the hydrogen producing apparatus of the present embodiment constructed as described above will be described below with reference to the flow charts shown in FIGS.

The controller 6 first detects the accelerator angle of the fuel cell vehicle in step 100, and calculates the required output of the fuel cell 4 in step 101. Then, referring to the map 102, in step 103, the required amount of ammonia for obtaining the required output is calculated.

Next, in steps 104 to 106, the controller 6 detects the temperature of the decomposer 2, the temperature of the combustor 3, and the hydrogen concentration in the exhaust gas discharged from the fuel cell 4, and the controller 6
In step 109, the necessary amount of ammonia is corrected and calculated from these values. That is, the degree of activation of the pellet catalyst 21, that is, the processing capacity of the decomposer 2 is determined by the temperature of the decomposer 2, and the degree of activation of the pellet catalyst 32 is determined by the temperature of the combustor 3.

If the hydrogen concentration in the exhaust gas from the fuel cell 4 is extremely reduced when the fuel cell 4 is in a high output state, the following problems will occur. That is, the decrease in the hydrogen concentration in the exhaust gas at the fuel-side electrode of the fuel cell 4 means that the hydrogen concentration in contact with the electrode surface decreases significantly from the inlet to the outlet, and the hydrogen concentration in contact with lean hydrogen is reduced. The generated electric power of the part that is shown is not enough. Further, when the amount of hydrogen supplied to the combustor 3 decreases, the calorific value in the combustor 3 becomes insufficient, the decomposition reaction in the decomposer 2 decreases, and the ammonia concentration in the decomposed gas supplied to the fuel cell 4 decreases. Increase and the power generation capacity is hindered.

Therefore, in this embodiment, in step 106, the concentration of hydrogen discharged from the fuel cell 4 is detected, and the controller 6
Performs the correction calculation of the amount of ammonia supplied to the decomposer 2 according to the value. The hydrogen concentration in the exhaust gas from the fuel cell 4 can be calculated by removing the hydrogen consumed for power generation from the hydrogen generated from the ammonia supply amount to the cracker 2. Alternatively, the hydrogen concentration in the exhaust gas of the fuel cell 4 can be directly detected. A thermal conductivity method can be used to directly detect the hydrogen concentration in the exhaust gas. In other words, the higher the hydrogen concentration in the gas, the greater the heat dissipation. Therefore, when a Pt wire that has been energized is inserted into the gas, the potential at both ends increases as the hydrogen concentration increases. Therefore, by obtaining the relationship in advance, the hydrogen concentration can be measured by measuring the potential of the Pt line. In this embodiment, the latter method is adopted.

When the correction amount due to the decomposition ability of the decomposer 2 and the correction amount due to the hydrogen concentration in the exhaust gas are contradictory,
The decomposition amount of the decomposer 2 is given priority over the correction amount by the decomposition ability of the decomposer 2.
It is desirable to maintain the ability of

Here, the temperature of the decomposer 2 is set to a predetermined value at the time of starting.
If it is lower than the value, the decomposition ability is below the specified value.
It is desirable not to supply ammonia to the decomposer 2. So
Here, in step 107, the temperature of the decomposer 2 is the predetermined value T₀ And ratio
And the temperature of the decomposer 2 is T ₀ Step only if above
 At 109, the correction amount and the supplied ammonia amount are calculated. If minutes
The temperature of the solver 2 is a predetermined value T₀ If lower, step
 At 108, ammonia is supplied to the combustor 3, and the combustion heat
The decomposer 2 is heated and the process returns to step 100.

In step 110, the amount of ammonia calculated in step 109 is supplied to the decomposer 2 and the fuel cell 4 operates. Then, the exhaust gas from the fuel cell 4 is supplied to the combustor 3, and a predetermined amount of air is supplied from the air supply means 5 to the combustor 3.
Is supplied to.

As described above, the amount of air supplied from the air supply means 5 to the combustor 3 must be determined as strictly as possible with respect to the combustible components in the exhaust gas from the fuel cell 4 without excess or deficiency. Therefore, in this embodiment, the control shown in FIG. 4 is performed.

That is, at step 200, the component concentration in the exhaust gas from the fuel cell 4 is calculated. As the hydrogen concentration in the exhaust gas from the fuel cell 4, the hydrogen concentration obtained in step 106 can be used, and the ammonia concentration can also be calculated from it. If ammonia is supplied in step 108, the amount is also added. Then, in step 201, the amount of air that burns the total amount of hydrogen and ammonia is calculated, and in step 202, the amount of air is supplied from the air supply means 5 to the combustor 3.

Subsequently, in step 203, the oxygen concentration in the exhaust gas of the combustor 3 is detected from the signal of the oxygen sensor 34, and in steps 204 to 205, when the oxygen concentration is lower than the predetermined value C, it is supplied to the combustor 3. The air supply means 5 is controlled so that the air amount is increased by ΔA, and when the oxygen concentration is higher than the predetermined value C, the air amount supplied to the combustor 3 is decreased by ΔA. As a result, the excess and deficiency of air can be eliminated on average, and the emission of nitrogen oxides and ammonia can be suppressed.

As the oxygen sensor 34, an oxygen concentration battery (galvanic cell) type sensor made of an oxygen ion conductor such as ZrO ₂ —Y ₂ O ₃ composite oxide, or a semiconductor type (TiO 2 type) whose resistance value changes with oxygen concentration is used. ₂ etc.) can be used.

When the detection output of the oxygen sensor 34 fluctuates as shown in FIG. 5 (a), an appropriate gradient of increase / decrease of the air amount is set as shown in FIG. It is possible to follow the time change of the exhaust gas. However, since the control point and the detection point are distant from each other in time and space, overshoot is inevitably generated. Therefore, as shown in FIG. 5C, the control delay can be reduced by adding a jump to the control value. Further, if a nonstoichiometric oxide such as cerium oxide or iron oxide is added to the pellet catalyst 32 of the combustor 3, the oxygen fluctuation can be alleviated by the oxygen absorbing / releasing ability, and the combustion activity is further improved.

When the drive of the automobile is stopped, the exhaust gas from the fuel cell 4 passes through the catalyst 41 by switching the valve 40, and ammonia and hydrogen are purified and discharged.

(Embodiment 2) In the above embodiment, the combustion heat in the combustor 3 is supplied to the decomposer 2. However, if the decomposer 2 is heated by another heating means, For example, the configuration shown in FIG. 6 may be used.

In this hydrogen producing apparatus, the decomposer 2 is heated by another heating means such as a heater, and therefore, the steps are the same as those in the first embodiment except that steps 104, 107 and 108 are not necessary in the flowchart of FIG. The combustion in the combustor 3 is controlled in the same manner as in Example 1 except that the temperature of the decomposer 2 is controlled. Further, the valves 30 and 40 in the first embodiment are unnecessary, and the exhaust gas of the combustor 3 can be discharged as it is even when the driving of the automobile is stopped.

[0069]

According to the hydrogen producing apparatus for a fuel cell of the present invention, hydrogen produced by decomposing a hydrogen source such as ammonia can be supplied to the fuel cell. Therefore, the hydrogen source can be easily installed in the automobile, and long-distance running can be performed with one filling. Further, since exhaust gas from the fuel cell is not discharged as it is, it is possible to prevent ammonia and the like from being discharged.

[Brief description of drawings]

FIG. 1 is a block diagram of a hydrogen production apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a decomposer and a combustor used in the hydrogen production device according to the embodiment of the present invention.

FIG. 3 is a flowchart showing the overall control in the hydrogen production device according to the embodiment of the present invention.

FIG. 4 is a flowchart showing the content of feedback control of the combustion air amount in the hydrogen production device according to the embodiment of the present invention.

FIG. 5 is a graph showing an example of control of the combustion air amount in the hydrogen production apparatus according to the embodiment of the present invention, and is a graph showing the relationship between time and the detection output of the oxygen sensor and the air amount.

FIG. 6 is a block diagram of a hydrogen production device according to another embodiment of the present invention.

[Explanation of symbols]

1: Ammonia cylinder 2: Decomposer 3: Combustor 4: Fuel cell 5: Air supply means 6: Control device 10: Supply device 34: Temperature sensor 41: Catalyst

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Claims (3)

[Claims] 1. A decomposer for decomposing a hydrogen source composed of at least one of ammonia and hydrazine into nitrogen and hydrogen by a catalytic reaction and supplying the same to a fuel cell; and a combustor for combusting exhaust gas from the fuel cell by a catalytic reaction. An air supply means for supplying combustion air to the combustor, an oxygen concentration detector for detecting the oxygen concentration in the exhaust gas from the combustor, and at least an oxygen concentration value detected by the oxygen concentration detector. And a control device for controlling the air supply means, and a hydrogen producing device for a fuel cell. 2. The hydrogen producing apparatus for a fuel cell according to claim 1, wherein the combustor supplies combustion heat of exhaust gas to the decomposer. 3. The hydrogen producing device for a fuel cell according to claim 1, wherein the fuel cell is operated at a temperature of 100 ° C. or higher.