JP2000319007A - Fuel reforming device and heat exchange device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel reforming device capable of rapidly performing heat exchange corresponding to load fluctuation and attaining rapid warming-up. SOLUTION: A hot storage tank 135 is provided in a reactor 131, in which the reforming reaction of fuel is performed, a recovery tank 136 is provided outside the reactor and the heat capacity of the reactor is made variable by changing the capacity of a heat storing material 138 housed in the heat storage tank. At the time of starting up of a system, the capacity of the heat storing material 138 housed in the heat storage tank 135 is decreased and when the system is stable, the capacity of the heat storing material 138 housed in the heat storage tank 135 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel reforming apparatus and a heat exchanging apparatus which are preferably used in a fuel cell system or the like, and more particularly to a fuel reforming apparatus and a heat exchanging apparatus which are suitable for applying heat to a site where a chemical reaction such as a fuel reforming reaction is performed. The present invention relates to a fuel reformer and a heat exchanger.

[0002]

2. Description of the Related Art It has been studied to cause a hydrogen-containing gas and an oxygen-containing gas to react electrochemically in the presence of a catalyst, and to use the generated power as a power source for an electric vehicle. In such a fuel cell, the hydrogen-containing gas is
For example, it can be produced by steam reforming a hydrocarbon such as methanol.

However, unlike a fuel reformer used in a chemical plant, a fuel reformer used for an electric vehicle frequently performs operations such as starting, stopping, accelerating or decelerating the vehicle. Load changes are frequent and large. That is, during rapid acceleration or on a slope, if the load suddenly increases and the amount of raw materials such as methanol to be reformed increases, the above-described steam reforming reaction is an endothermic reaction. Rapidly decreases, and accordingly, the reaction efficiency also decreases.

[0004] For this reason, it is necessary to compensate for the insufficient amount of heat from the outside in a short period of time with good responsiveness in accordance with the load fluctuation of the vehicle. This can be dealt with by increasing the heat capacity of the part where the heat occurs. For example, JP-A-9-306
In the heat exchange device disclosed in Japanese Patent Publication No. 533, it is proposed to use latent heat of a heat storage material.

[0005]

However, in the above-described heat exchange device or fuel reforming device, the heat capacity of the reforming reaction portion including the latent heat of the heat storage material is remarkably large. In addition, there has been a problem that the time required to raise the temperature of the reforming reaction portion to a predetermined temperature, that is, the warm-up time becomes long.

[0006] The present invention has been made in view of such problems of the prior art, and a heat exchange apparatus and a fuel reforming apparatus capable of quickly achieving heat exchange with respect to load fluctuations and realizing quick warm-up. The purpose is to provide.

[0007]

According to a first aspect of the present invention, there is provided a fuel reforming apparatus according to the first aspect of the present invention, wherein a fuel reforming reaction is carried out in a reactor in which a fuel reforming reaction is performed. A heat storage unit is provided, and the heat capacity of the heat storage unit is variable.

[0008] The specific constitution of the above invention is not particularly limited, but in the fuel reforming apparatus according to the second aspect, a heat storage tank provided inside the reactor and a heat storage tank provided outside the reactor are connected. And a pump for controlling the capacity of the heat storage material contained in the heat storage tank.

In the above invention, the specific configuration of the variable control of the heat capacity of the heat storage unit is not particularly limited, but in the fuel reformer according to the third aspect, the capacity of the heat storage material stored in the heat storage tank is reduced at the time of startup. When the temperature is stable, the capacity of the heat storage material stored in the heat storage tank is increased.

In the fuel reforming apparatus according to any one of the first to third aspects, since a heat storage section having a variable heat capacity is provided in the reactor in which the fuel reforming reaction is performed, it is necessary to supply heat. By reducing the heat capacity of the heat storage unit when the system is started, the fuel reforming reaction is stabilized in a short time. In addition, by increasing the heat capacity of the heat storage unit when the system is stable, even if a sudden load change occurs, it can be sufficiently absorbed. Therefore, the warm-up operation time of the fuel reformer can be shortened, and a load change can be appropriately dealt with without interrupting the fuel reforming reaction.

In the above invention, the heat storage material supplied to the heat storage section can be heated by the fuel reforming reaction itself performed in the reactor (internal heating system).
In addition, the fuel reforming apparatus according to claim 4 is characterized by further comprising heating means for preheating the heat storage material supplied to the heat storage section.

[0012] The heat storage material is preheated using the amount of heat of a combustor or the like added to the fuel reformer, and is supplied to the heat storage section of the reactor (external heating method), so that the heat utilization efficiency of the system is improved. Better.

Although not particularly limited in the above invention,
In the fuel reformer according to claim 5, after the stop, at least while the temperature of the heat storage unit is equal to or higher than a predetermined temperature,
The heat capacity of the heat storage unit is maintained as it is.

If a sufficient amount of heat is stored in the heat storage unit even after the system is stopped, the heat storage material can be used as a heat insulating material by maintaining the heat amount as it is. There is no need to warm up when starting up,
The fuel reforming reaction can be started immediately.

In the above invention, the fuel reforming reaction can be applied to an autothermal reformer using a steam reforming reaction and a partial oxidation reaction, or a steam reformer using only a steam reforming reaction. The present invention can be applied to a fuel reforming apparatus using other reforming reactions.

(2) In order to achieve the above object, the heat exchanger according to claim 6 according to the second aspect of the present invention is provided with a heat storage section at a portion where heat exchange is performed, and the heat capacity of the heat storage section is provided. Is variable.

The present invention is applicable not only to the above-described fuel reforming apparatus but also to a shift reaction apparatus and a selective oxidation reaction apparatus for removing carbon monoxide from a hydrogen-containing gas generated by the fuel reforming apparatus. , Can be applied as a heat exchange device. Further, in addition to a reaction device involving such a chemical reaction, the present invention can be applied as an evaporator or a normal heat exchange device.

[0018]

According to the first to third and sixth aspects of the invention, the fuel reforming reaction can be performed in a short time by reducing the heat capacity of the heat storage unit at the time of startup of the system requiring the supply of heat. On the other hand, when the system is stable, by increasing the heat capacity of the heat storage unit, even if a sudden load change occurs, it can be sufficiently absorbed. As a result, the warm-up operation time of the fuel reformer can be shortened, and a load change can be appropriately dealt with without interrupting the fuel reforming reaction.

In addition, according to the fourth aspect of the present invention, the heat storage material is preheated by utilizing the amount of heat of the combustor or the like added to the fuel reformer, and is supplied to the heat storage section of the reactor. Therefore, the heat utilization efficiency of the system is further improved.

Further, according to the fifth aspect of the present invention, the heat storage material can be used as a heat retaining material, and it is not necessary to perform a warm-up operation at the next startup, and the fuel reforming reaction is immediately started. be able to.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment FIG. 1 is a block diagram showing an example of a fuel cell system to which a fuel reformer of the present invention is applied, and FIGS. 2 and 3 are cross-sectional views showing an embodiment of the fuel reformer of the present invention. .

First, the configuration of the fuel cell system 1 according to the present embodiment will be described with reference to FIG. 1. The fuel cell system 1 according to the present embodiment includes counter electrodes 112 and 113 with an electrolyte 111 interposed therebetween. Fuel cell 11,
Compressed air (oxygen-containing gas) from the compressor 12 is supplied to the cathode 112 side of the fuel cell 11 and the anode 113
The hydrogen-containing gas from the reformer 13 is supplied to the side. These supply pipes are indicated by 191 and 192, respectively.

The compressor 12 takes in outside air and compresses it to about 2 kg / cm ^2,
The type is not particularly limited, and a piston compressor, a scroll compressor, a turbo compressor, or the like can be used. The air supplied to the fuel cell 11 is preferably at a temperature of 80 to 85 ° C., but the air compressed by the compressor 12 is at about 170 ° C. It is desirable to provide an intercooler (not shown) in the pipe 191 between the fuel cell 12 and the fuel cell 11.
As the intercooler, any of a water-cooled type and an air-cooled type can be used.

On the other hand, the reformer 13 mixes, for example, methanol (reforming raw material), steam and air (oxygen-containing gas), and makes a hydrogen-rich gas by a steam reforming reaction and an oxidation reaction of methanol. A so-called auto-thermal reformer that can omit or reduce the capacity of a separate heater by covering the amount of heat required for the steam reaction (endothermic reaction) with the amount of heat generated by the oxidation reaction (exothermic reaction). is there.

Methanol as a reforming raw material is accommodated in a methanol tank 14 and pumped by a pump 16 to the evaporator 1.
8 where it is vaporized. The water vapor stored in the water tank 15 is supplied to the evaporator 18 by the pump 17.
, Where it is vaporized into steam. The methanol gas and the steam are sent to the inlet 132 of the reformer 13, and the air is combined from the compressor 12 and supplied.

In the steam reforming reaction of methanol in the reformer 13, the decomposition reaction of methanol and the modification reaction of carbon monoxide represented by the following formulas are simultaneously progressed by receiving the supply of methanol and steam to produce hydrogen and carbon dioxide. Is generated.

[0027]

Embedded image Methanol reaction: CH ₃ OH → CO + 2H ₂ -9
0.0 kJ / mol Denaturation reaction: CO + H ₂ O → CO ₂ + H ₂ +
40.5 kJ / mol Overall reaction: CH ₃ OH + H ₂ O → CO ₂ +
3H ₂ -49.5 kJ / mol On the other hand, in the oxidation reaction of methanol, a reformed gas containing hydrogen and carbon dioxide is generated by the oxidation reaction shown in the following formula by supplying methanol and air.

[0028]

Embedded image Oxidation reaction: CH ₃ OH + 1 / 2O ₂ → 2H
₂ + CO ₂ +189.5 kJ / mol If the fuel gas supplied from the reformer 13 to the anode 113 side of the fuel cell 11 contains carbon monoxide, the fuel cell 11 is poisoned. It is desirable to provide a device for reducing the content of carbon monoxide in the piping between the fuel cell 13 and the fuel cell 11. This carbon monoxide reduction device
Unreacted carbon monoxide and water in the reformed gas obtained in the reformer 13 are subjected to the same modification reaction (CO + H ₂ O → CO ₂ + H
₂ ) a shifter that generates a fuel gas having a high hydrogen content by being transformed into hydrogen and carbon dioxide, and further selectively oxidizes carbon monoxide contained in the reformed gas that has passed through the shifter to obtain (CO + 1) / 2O ₂ → CO ₂ ) and the like.

As shown in FIG. 2, the reformer 13 is a cylindrical reactor 131 having an inlet 132 and an outlet 133 formed therein.
The above-mentioned mixed gas of methanol gas, steam and air is introduced from the inlet 132, and when passing through the catalyst 134, the above-mentioned steam reforming reaction and partial oxidation reaction occur. The generated hydrogen-rich gas is supplied from the outlet 133 to the fuel cell 11.

The catalyst 134 accommodated in the reactor 131
A copper-based catalyst such as Cu-Zn, a noble metal such as Pt or Pd, or a Group VIII-based metal catalyst such as Ni is attached to a monolith in which holes having a triangular, square or hexagonal cross-sectional shape are formed in a honeycomb shape. It is a thing. Such a catalyst is referred to as a monolith catalyst, but the reformer 13 of the present invention, in addition to the monolith catalyst, is formed by pelletizing the above-mentioned copper-based catalyst such as Cu-Zn into the reactor 131. A pellet catalyst can also be applied.

In particular, in the reformer 13 of the present embodiment, a heat storage tank 135 is provided inside the
Recovery tank 1 communicating with heat storage tank 135 outside of 31
36, and a pump 137 is provided between them. The heat storage tank 135 contains a heat storage material 138 such as silicone oil, for example.
6 can be moved.

For example, as shown in FIG. 2, the warm-up operation is desirably performed with the heat storage tank 135 empty. In the case of the above-mentioned autothermal reformer, the warm-up operation is performed under operating conditions in which the heat generation amount of the partial oxidation reaction is higher than the endothermic amount of the steam reforming reaction, and in some cases, the operation condition of only the partial oxidation reaction. . By the way, until the reformer itself reaches the predetermined temperature, a sufficient amount and quality of reformed gas cannot be obtained, and unreacted fuel and undesired components such as carbon monoxide are not allowed in the fuel cell. Since the above is included, it cannot be used for power generation by the fuel cell. Insufficient quantity and quality of reformed gas is burned in a combustor, and this heat is recovered and used.

When the warm-up operation is performed with the heat storage tank 135 empty as described above, the heat capacity of the reactor 131 is reduced, so that the temperature is quickly raised and the warm-up time is shortened. When the heat capacity of the reactor 131 is small as described above, it is not possible to sufficiently cope with a sudden load change.

For this reason, when the temperature of the reactor 131 rises to a predetermined temperature, the pump 137 is operated to remove the heat storage material 138 of the recovery tank 136 from the heat storage tank 135 as shown in FIG.
Inject into. At this time, under the operating condition in which the heat generation amount of the partial oxidation reaction is larger than the heat absorption amount of the steam reforming reaction, the heat storage material 138 is injected into the heat storage tank 135 so that the temperature does not rise excessively from a predetermined temperature. When the tank 135 becomes full, the injection of the heat storage material 138 is stopped, and under the operating conditions of a so-called ordinary autothermal reformer in which the endothermic amount of the steam reforming reaction and the calorific value of the partial oxidation reaction are balanced. The reformer 13 is operated.

As described above, the heat storage material 13 is stored in the heat storage tank 135.
In the state in which the load 8 is filled, the heat capacity of the reactor 131 is large, so that the reactor becomes extremely stable, and even if a sudden load change occurs, the temperature may rise too much or the temperature may fall too much. As a result, the amount and quality of the reformed gas are suppressed from being reduced.

Next, a stop sequence and a start sequence of the reformer 13 according to the present embodiment will be described with reference to FIGS. FIG. 6 is a flowchart showing a stop sequence of the reformer 13 of the present embodiment.
In a state where the supply of the raw material gas (for example, methanol gas, water vapor and air) to the inlet 132 of the fuel cell 31 is stopped to stop the reforming reaction, the heat storage tank 135 is filled with the heat storage material 138. After the reformer 13 is stopped, the temperature Tr of the catalyst 134 provided in the reactor 131 is read (step 1). If the temperature Tr is higher than a predetermined threshold temperature Tmin, the temperature is kept as it is. When the temperature Tr of the catalyst 134 becomes equal to or lower than the predetermined temperature Tmin, the heat storage material 138 in the heat storage tank 135 is recovered to the recovery tank 136 (steps 2 and 3).

As described above, when the catalyst temperature Tr of the reactor 131 is sufficiently high, the heat storage material 13 is stored in the heat storage tank 135.
Since the value of 8 is satisfied, the heat capacity of the reactor itself is increased, and a heat retaining function is achieved. Therefore, the time required for the warm-up operation when the system is restarted can be shortened, the energy required for the warm-up can be saved, and the energy efficiency can be improved. In particular, when the stop time of the system is short, the reforming reaction can be started without performing the warm-up operation.

The above-mentioned threshold temperature Tmin may be a temperature at which the heat storage material 138 loses the heat retaining function, for example, a lower limit temperature at which a reforming reaction can be performed. Alternatively, a lower limit temperature that satisfies the condition that the time required for the warm-up operation to reach that temperature is longer than the time required for recovering the heat storage material 138 may be adopted.

FIG. 7 is a flowchart showing a start-up sequence of the reformer 13 of this embodiment.
At the time, the temperature Tr of the catalyst 134 in the reactor 131 is read, and the lower limit temperature T at which the above-described reforming reaction can be performed.
min (step 2). As described in the stop sequence of FIG. 6, the catalyst temperature Tr becomes the lower limit temperature Tmi.
If the temperature is higher than n, the heat storage material 138 is full in the heat storage tank 135, and the heat capacity of the reactor 131 is higher than the lower limit temperature at which the reforming reaction can be performed. The reforming reaction is started by injecting gas (step 3).

If the catalyst temperature Tr in step 3 is lower than the lower limit temperature Tmin, the raw material gas is supplied to the reactor because the heat storage tank 135 is empty as described in the stop sequence in FIG. Then, the warm-up operation is started (step 4), and the catalyst temperature Tr is reduced to the lower limit temperature Tmi.
Continue until it becomes higher than n (steps 5 and 6). This warm-up operation is performed under operating conditions in which the heat value of the partial oxidation reaction is larger than the heat absorption amount of the steam reforming reaction, and in some cases, the operating condition of only the partial oxidation reaction.
Unreacted fuel gas, carbon monoxide gas and the like discharged from 3 are supplied to a combustor or the like.

When the catalyst temperature Tr becomes higher than the lower limit temperature Tmin in step 6, a reforming gas of sufficient quality and quantity can be obtained, and thus a reforming reaction is started (step 7). At this time, the heat storage material 138 is injected into the heat storage tank 135 so that the temperature does not rise excessively from a predetermined temperature under operating conditions in which the heat generation amount of the partial oxidation reaction is larger than the heat absorption amount of the steam reforming reaction ( Step 8) When the heat storage tank 135 is full (Step 9), the injection of the heat storage material 138 is stopped, and the so-called normal auto-recovery is performed, where the heat absorption of the steam reforming reaction and the heat generation of the partial oxidation reaction are balanced. Reformer 1 under operating condition of thermal reformer
3 is operated (step 10).

Second Embodiment FIG. 4 is a sectional view showing another embodiment of the fuel reformer of the present invention, which is an autothermal reformer 13 similar to the first embodiment described above. In one embodiment, the heat storage material 138 in the heat storage tank 135 is heated by the reaction heat of the reactor 131.
In this embodiment, the reformer 13 includes a combustor 20 and heats the heat storage material 138 using the heat of the combustor 20.

That is, a pipe connecting the heat storage tank 135 and the recovery tank 136 is delivered to the inside of the combustion pipe 201 of the combustor 20, and the heat exchange section 202 is formed here. Therefore, the pump 137 is operated to operate the collection tank 1.
When the heat storage material 138 in the storage 36 is pressure-fed to the heat storage tank 136, the heat storage material 138 is heated by the heat exchange unit 202 of the combustor 20 before that.
The high-temperature heat storage material is supplied to the heat storage tank 135.
Accordingly, when the heat storage material 138 is injected as in the first embodiment, it is not necessary to operate under the condition that the heat generation amount of the partial oxidation reaction is higher than the heat absorption amount of the steam reforming reaction. The operating conditions of the type reformer can be used.

Third Embodiment FIG. 5 is a cross-sectional view showing still another embodiment of the fuel reformer of the present invention, which is not an autothermal reformer as in the first and second embodiments described above. And a steam reformer that performs only a steam reforming reaction. Since this steam reforming reaction is an endothermic reaction as can be seen from the above-described reaction formula, a heat exchange unit 139 for heating the catalyst 134 is provided inside the reactor 131, and the heat exchange unit 139 is provided.
Is connected to a heat exchange section 203 provided inside the combustor 20, whereby heat in the combustor 20 is transferred to the reactor 13.
1 is transmitted. “204” is a pump for pumping the heat transport medium.

Then, similarly to the second embodiment, a pipe connecting the heat storage tank 135 and the recovery tank 136 is delivered to the inside of the combustion tube 201 of the combustor 20, and the heat exchange section 202 is formed here. . Therefore, the pump 137
When the heat storage material 138 in the recovery tank 136 is sent to the heat storage tank 136 by pressure, the heat storage material heated by the heat exchange unit 202 of the combustor 20 and having a high temperature is supplied to the heat storage tank 135. Accordingly, when the heat storage material 138 is injected, it is not necessary to operate under the condition that exceeds the heat absorption amount of the steam reforming reaction, and the operating condition of the ordinary steam reforming type reformer can be used as it is.

The embodiments described above are described for facilitating the understanding of the present invention, but are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, the shape of the heat storage tank 135 provided in the reactor 131 is only schematically shown in FIGS. 2 to 5, and is not limited to these shapes. Further, fins may be provided on the surface of the heat storage tank or the like in order to enhance the heat exchange property.

Further, the reformer of the present invention is not limited to the above-described autothermal type or steam reforming type, and may be a reformer using another reforming method. Also,
The present invention can be applied not only to a reforming reactor but also to a shift reactor and a carbon monoxide selective oxidizer, and can also be applied to a reformer in which these are integrated. Furthermore, the present invention can be applied to an evaporator or a heat exchanger that does not involve a chemical reaction.

The heat storage material according to the present invention may be a liquid metal such as mercury, a liquid metal such as sodium such as sodium, or a phase transition near the operating temperature such as lithium nitrate in addition to the silicone oil described above. Salt may be used. When a heat storage material that is solid at room temperature is used, the material is phase-transformed into a liquid and then transported. When the system is stopped, the heat storage material is collected before the phase is converted into a solid. Moreover, you may comprise so that a solid heat storage material may be inserted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a fuel cell system to which a fuel reforming apparatus of the present invention is applied.

FIG. 2 is a sectional view showing an embodiment of the fuel reforming apparatus of the present invention.

FIG. 3 is a sectional view showing the operation of the embodiment shown in FIG. 2;

FIG. 4 is a sectional view showing another embodiment of the fuel reforming apparatus of the present invention.

FIG. 5 is a sectional view showing another embodiment of the fuel reforming apparatus of the present invention.

FIG. 6 is a flowchart showing processing when the fuel reforming apparatus of the present invention is stopped.

FIG. 7 is a flowchart showing a process at the time of starting the fuel reforming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 11 ... Fuel cell 12 ... Compressor 13 ... Reformer (fuel reformer) 131 ... Reactor 132 ... Inlet 133 ... Outlet 134 ... Catalyst 135 ... Heat storage tank 136 ... Recovery tank 137 ... Pump 138 ... Heat storage Material 14: Methanol tank 15: Water tank 16, 17 ... Pump 18: Evaporator 20: Combustor

Claims (6)

[Claims] 1. A fuel reformer, wherein a heat storage section is provided in a reactor in which a fuel reforming reaction is performed, and the heat capacity of the heat storage section is variable. 2. A heat storage tank provided in the reactor,
2. The fuel reformer according to claim 1, further comprising: a recovery tank provided outside the reactor and connected to the heat storage tank; and a pump for controlling a capacity of a heat storage material accommodated in the heat storage tank. 3. apparatus. 3. The fuel reformer according to claim 2, wherein the capacity of the heat storage material stored in the heat storage tank is reduced at the time of start-up, and the capacity of the heat storage material stored in the heat storage tank is increased at the time of stability. Quality equipment. 4. The apparatus according to claim 1, further comprising heating means for preheating the heat storage material supplied to said heat storage section.
The fuel reformer according to any one of the above. 5. The heat capacity of the heat storage unit is maintained as it is, at least as long as the temperature of the heat storage unit is equal to or higher than a predetermined temperature after the stop.
5. The fuel reforming apparatus according to any one of 4. 6. A heat exchange device wherein a heat storage section is provided at a portion where heat exchange is performed, and a heat capacity of the heat storage section is variable.