JP2002211906A - Hydrogen producing system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the miniaturization of a reforming unit of a raw material, the improvement of starting-up performance and a wide operation range. SOLUTION: A reforming unit 100 producing hydrogen by reforming a raw material such as gasoline is formed by a parallel structure of a plurality of sub-reforming units 110-190. Each reforming sub-unit is provided with a reforming part 113 performing steam reforming, shift reaction parts 115 and 117 each performing shift reaction and a CO oxidization part 118 separately. Each sub-reforming unit is miniaturized by being adapted to the reaction at a relatively high space velocity. At the time of starting-up the reforming unit, the rapid warming up is attained by reducing the operating number of the sub-reforming units to suppress the heat capacity. At the time of operating, the quantity of produced hydrogen is changed and wide operation range is secured without largely changing the space velocity of the sub-reforming reaction unit by exchanging the operation number of the sub-reforming units corresponding to the required hydrogen quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a hydrogen generation system for generating a hydrogen-rich gas by reforming a raw material.

[0002]

2. Description of the Related Art A fuel cell generates power by an electrochemical reaction between hydrogen supplied to an anode and oxygen supplied to a cathode. Hydrogen supplied to the anode is generated, for example, by reforming a raw material. In this case, natural gas, gasoline and other hydrocarbon-based compounds, alcohols, ethers, aldehydes and the like are generally used as raw materials.

[0003] Raw material reforming is performed in multiple stages. The first stage is a reaction in which hydrogen and carbon monoxide are generated by a reaction between a raw material and steam or oxygen. The former is called a steam reforming reaction, and the latter is called a partial oxidation reaction. The second stage is a reaction for producing hydrogen and carbon dioxide from the carbon monoxide and water produced here. This reaction is called a shift reaction.
In order to purify the remaining carbon monoxide that has not been treated by these reactions, a third-stage reaction may be performed by burning or selectively oxidizing carbon monoxide. These reactions are performed in an appropriate combination depending on the type of the raw material and the like. For example, when alcohol is used as a raw material, the shift reaction may be omitted.

FIG. 13 is a perspective view showing a conventional raw material reforming unit. The raw material is vaporized and introduced into the unit together with water vapor in the direction indicated by the arrow. The input raw material is mixed with steam in the mixing section 10 and steam reformed in the reforming section 11. The reforming unit 11 is a structure in which a reforming catalyst is supported on a honeycomb or the like. The gas generated by the steam reforming is cooled slightly in the heat exchanger 12 and supplied to the shift reaction units 13 and 15. Shift reaction units 13 and 15
Are structures in which a catalyst for a shift reaction is supported on a honeycomb or the like. Between the shift reaction units 13 and 15,
A heat exchanger 14 is provided to adjust the temperature of the gas to a state suitable for the reaction. The gas that has undergone the shift reaction is supplied to the CO purification unit 16 located at the most downstream side. CO
The purifying unit 16 carries a catalyst for selectively oxidizing carbon monoxide. The raw material is reformed into a hydrogen-rich gas by the above units.

[0005] The capacity of the reforming reaction depends on the space velocity SV (Space SV).
Velocity). The space velocity SV refers to the volume of gas that can react with a unit volume of catalyst in unit time. The higher the space velocity SV, the higher the capability of the reforming reaction, which means that a large amount of hydrogen can be generated in a short time. The space velocity SV is affected by the reaction conditions such as the type of catalyst used for the reaction, the temperature and the pressure. The size of the reforming unit is set according to the required amount of hydrogen based on the achievable space velocity SV.

[0006]

Heretofore, there has been a problem with the reforming unit in terms of improving startability and reducing the size.
Also, it has been required to secure a wide operating range. The operating range refers to a variable range of the amount of hydrogen generated per unit time.

[0007] Improving the startability means reducing the time required from the start of operation of the reforming unit to the start of hydrogen generation. Startability is affected by the time required for warming up the catalyst in the reforming unit, that is, the heat capacity of the entire reforming unit.
In order to improve the startability, it is preferable to reduce the heat capacity. On the other hand, miniaturization is realized by improving the space velocity SV. In recent years, attempts have been made to mount a reforming unit and a fuel cell on a moving body such as a vehicle, and in such a case, there has been a particularly strong demand for miniaturization, startability, and securing an operating range.

However, it has been found that when the space velocity SV is increased to reduce the size of the reforming unit, it is difficult to secure a wide operating range. It is generally known that when the maximum value of the space velocity SV that can be realized is increased, the stability of a reaction in a state where the space velocity SV is low extremely decreases. In order to secure a wide operating range and to maintain the reaction efficiency in a state where the space velocity SV is low, the upper limit of the space velocity SV is actually limited. With the upper limit of the space velocity SV limited, in order to generate a sufficient amount of hydrogen,
It was necessary to increase the volume of the reforming unit. Since an increase in volume leads to an increase in heat capacity, the increase in volume impairs not only the size of the reforming unit but also the startability.

As described above, conventionally, it has been difficult to achieve both startability and miniaturization of the apparatus while ensuring a wide operating range. An object of the present invention is to improve startability, reduce the size of a device, and secure a wide operating range in a hydrogen generation system for reforming a raw material.

[0010]

Means for Solving the Problems and Actions and Effects Thereof To solve at least a part of the above-mentioned problems, the present invention employs a configuration in which a hydrogen generating system includes a chemical reaction section, an adjustment mechanism, and a control section. The chemical reaction section is a unit that performs a chemical reaction of the raw materials. As a raw material, natural gas, gasoline and other hydrocarbon compounds, alcohols, ethers, aldehydes and the like are generally used. The chemical reaction includes these steam reforming, partial oxidation reaction, shift reaction, selective oxidation reaction of carbon monoxide, and the like. Some or all of these reactions are selected depending on the type of raw materials.

The adjusting mechanism is a mechanism capable of adjusting at least one of the heat capacity and the volume of the chemical reaction section. The control unit changes at least one of the heat capacity and the volume according to the operation state required for the system. Characteristics such as system bootability, size, and operating range are all related to heat capacity,
Since the present invention is closely related to the volume, the present invention can improve the characteristics by changing these according to the operating state. Adjusting the volume means adjusting a portion functioning as a chemical reaction unit, and also adjusting the catalyst used for the reaction together with the volume.

An example of control of the heat capacity and the like in the present invention will be described. For example, a mode in which the heat capacity or the like is controlled depending on whether the system is in a warm-up state can be adopted. If the heat capacity or volume is reduced during warm-up, the temperature of the system can be quickly raised, and the time required for warm-up can be reduced.

As another aspect, the volume and the like may be controlled in accordance with the required amount of hydrogen. By changing the volume of the chemical reaction section, it is possible to control the amount of generated hydrogen without significantly changing the space velocity SV. In addition, by adjusting the heat capacity in accordance with the required amount, it is possible to avoid a temperature change in the chemical reaction section caused by a change in the amount of the supplied raw material, and to stabilize the reaction. In other words, by changing the volume or the like according to the required amount of hydrogen, it is possible to easily secure a wide operating range while operating the chemical reaction section at a relatively high space velocity SV.

The heat capacity and the volume can be adjusted, for example, by providing a plurality of sub-chemical reaction sections for performing the same chemical reaction in parallel and switching the number of operating sub-chemical reaction sections used for the reaction. In this case, the adjustment mechanism is a mechanism capable of switching the number of operations. For example, it can be constituted by a pipe and a valve for individually adjusting the supply of the raw material to each sub-chemical reaction section. In addition, the volume of the chemical reaction section itself may be made variable, or the heat capacity may be made variable by covering the chemical reaction section with a heat medium and changing the amount thereof.

The switching of the number of operations can be carried out, for example, by increasing the required number of hydrogen and increasing the number of operations. Since an increase in the number of operating units means an increase in the total volume of the sub-chemical reaction section, the amount of hydrogen generated can be increased even when the space velocity SV is constant. By reducing the number of operations according to the required amount of hydrogen, it is possible to suppress the amount of hydrogen generated while the space velocity SV remains high. An increase in the number of operating units means an increase in the heat capacity of the entire sub-chemical reaction section at the same time.
The reaction can be stabilized. Therefore, by switching the number of operations, it is possible to secure a wide operating range while achieving downsizing by the high space velocity SV.

The operating number may be switched by turning each sub-chemical reaction section on and off, but the amount of raw material supplied to each sub-chemical reaction section according to the required amount of hydrogen, in other words, each sub-chemical reaction section The number of operations may be switched while controlling the output of the unit. For example, the following two-stage control can be performed. In the first stage, the amount of generated hydrogen is increased by increasing the number of operations while supplying a relatively small amount of raw material to each sub-chemical reaction section. After all the sub-chemical reaction sections are in operation, the second stage control is started, and the supply amount of the raw material to each sub-chemical reaction section is increased to the maximum value. In this way, by controlling the amount of the raw material supplied to the sub-chemical reaction section and the number of operations in combination, the amount of generated hydrogen can be switched in small increments. Various combinations of the output and the number of operations other than those exemplified here are possible.

When a part of the sub-chemical reaction section is operated, the simplest control is to continuously operate a certain sub-chemical reaction section. In this case, it is desirable to separately provide a configuration for maintaining the warm-up state of the sub-chemical reaction unit that is not operated.

On the other hand, the sub-chemical reaction section used for the reaction may be switched at a predetermined timing. When switching, it is preferable to maintain the relationship between the required amount of hydrogen and the number of operations. This makes it possible to maintain the warm-up state of each sub-chemical reaction section relatively easily. The switching timing may be set in advance based on the heat capacity or the like of the sub-chemical reaction unit in consideration of maintaining the warm-up state. The timing may be constant, or the timing may be changed according to the required amount of hydrogen or the like.

The sub-chemical reaction section can have various configurations. In particular, the sub-chemical reaction section is configured to have a polygonal cross-sectional shape perpendicular to the gas flow direction, and the sub-chemical reaction sections are close to each other on the sides of the polygon. It is desirable to arrange them. In this way, the sub-chemical reaction section can be accumulated in a relatively small volume,
The size of the device can be reduced.

The sub-chemical reaction section having a polygonal cross section is preferably applied to a unit for performing a shift reaction for generating hydrogen from carbon monoxide and water. In general, the shift reaction is known to have a lower reaction rate than steam reforming, etc.
A relatively large volume is required to generate the required amount of hydrogen. If a polygonal cross-sectional shape is applied to a portion requiring a volume in this manner, the volume can be secured while reducing the size of the whole.

The sub-chemical reaction section may be applied to only a part of the chemical reaction section. For example, when the chemical reaction unit is composed of multi-stage units that perform different chemical reactions, a part on the upstream side is configured as a sub-chemical reaction unit, and the remaining part on the downstream side is shared by a plurality of sub-chemical reaction units. It can be configured as a shared reaction section.

It is desirable that the upstream sub-chemical reaction section includes at least a reforming section for performing steam reforming or partial oxidation reaction of the raw material. The advantage of the sub-chemical reaction section is that the sub-chemical reaction section is suitable for a reaction capable of realizing a high space velocity SV, and is therefore highly useful for the reforming section.

It is preferable that the shared reaction section includes a shift reaction section for performing a shift reaction for generating hydrogen from carbon monoxide and water in the gas generated in the sub-chemical reaction section. As described above, the shift reaction section requires a relatively large volume. Therefore, if the shift reaction unit is shared, a sufficient volume can be easily secured in the shift reaction unit even when the upstream sub-chemical reaction unit is partially operating. For the same reason, it is preferable that the shared reaction section includes an oxidation reaction section for oxidizing carbon monoxide in the gas generated in the sub-chemical reaction section.

When sub-chemical reaction sections are used, it is desirable to provide a heat insulating layer between the sub-chemical reaction sections to suppress mutual heat transfer in order to avoid wasteful release of heat in each sub-chemical reaction section. .

The heat insulating layer may have a heat insulating material such as ceramics interposed, or may have a gap between the sub-chemical reaction sections. When a gap is provided, it is more desirable to seal the entire chemical reaction section in order to suppress air convection.

When a gap is provided, it is desirable to further provide a heat supply unit for supplying heat for heating the sub-chemical reaction section to the gap. The supply of heat may be performed by a heater or the like, or may be configured to supply a fluid for warming up the sub-chemical reaction section to the gap. The fluid may be a gas or a liquid. For example, exhaust gas from an evaporator that vaporizes a raw material, exhaust gas from a fuel cell that consumes generated hydrogen, and the like can be used.

The present invention can be configured in various modes, such as a configuration of the hydrogen generation system and an operation method of the system. In the present invention, the consumption system of the generated hydrogen is not limited. However, as an example, the present invention may be configured as a fuel cell system in which the above-described hydrogen generation system and a fuel cell are combined. The fuel cell system thus configured has features of small size, high startability, and a wide operating range, and thus has high utility for mounting on vehicles and other moving objects.

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below on the basis of examples with the following items. A. System configuration: B. Configuration of reforming unit: B1. Modification of Modification Unit (1): B2. Modification example (2) of reforming unit: Reforming control: C1. Modification example (1) of reforming control: C2. Modification of Modification (2):

A. System Configuration: FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system as an embodiment. The fuel cell system according to the present embodiment may be configured as any of a stationary system and a system mounted on a moving body such as a vehicle. As will be described later, the system of the present embodiment has characteristics such as small size, high startability, and a wide operating range, and thus is particularly useful as an on-board system.

The fuel cell 20 generates electric power by receiving supply of hydrogen and oxygen. Various types can be applied to the fuel cell 20, but in this embodiment, a solid polymer type was adopted.
Oxygen for power generation is provided by air. Hydrogen is generated by reforming a raw material by a hydrogen generation system.
After the air and the hydrogen are provided for power generation by the fuel cell 20,
It is supplied into a reforming unit 100 described later.

The configuration of the hydrogen generation system is as follows. The raw material and water used for the reforming are stored in a raw material tank 11 and a water tank 12, respectively. As a raw material, generally, natural gas, gasoline and other hydrocarbon compounds, alcohols, ethers, aldehydes and the like can be used. The raw material and water are each vaporized by the evaporator 15 and supplied to the reforming unit 100. The supply amounts of the raw material and water can be adjusted by valves 13 and 14 provided in the piping. These valves 13 and 14 are
It is controlled by the control unit 10 as described later.

The reforming unit 100 is covered with a case 102. Inside the reforming unit 100, nine sets of sub-reforming units 110 to 190 having the same configuration and the supply amounts of raw materials and water to each unit are adjusted. Are provided in parallel. The configuration of each sub-reforming unit will be described later.

The operation of the entire fuel cell system is controlled by the control unit 10. The control unit 10 is configured as a microcomputer including a CPU, a RAM, a ROM, and the like inside. The control unit 10 electronically controls the opening of each of the valves 13, 14, 111 to 191 described above. The control unit 10 also controls the operation of the evaporator 15, the power generation of the fuel cell 20, and the like. To realize these controls, various signals are input to the control unit 10, but they are not shown in the present embodiment.

B. Configuration of Reforming Unit: FIG. 2 is a perspective view of the reforming unit 100. Illustration of the case 102 and the valves 111 to 191 is omitted. Sub reforming unit 1
10 to 190 have a square cross-sectional shape, and are arranged three by three in the up, down, left, and right directions. A space with a distance d is provided between each sub-reforming unit.
The respective configurations will be described with the sub-reforming unit 110 as a representative.

In the sub-reforming unit 110, the vaporized raw material and steam are introduced into the mixing section 112. Both are mixed here to have a nearly uniform distribution,
It flows into the reforming section 113. The reforming unit 113 is a unit that performs the steam reforming of the raw material and the partial oxidation reaction in parallel, and has a structure in which a catalyst suitable for this reaction is supported on a honeycomb or the like. While passing through the reforming section 113, the raw material is reformed by the action of a catalyst to generate hydrogen and carbon monoxide.

The gas generated in the reforming section 113 passes through the heat exchanger 114 and flows into the high-temperature shift reaction section 115.
The high-temperature shift reaction unit 115 is a unit that performs a shift reaction of generating hydrogen and carbon dioxide from carbon monoxide and water, and has a structure in which a catalyst suitable for this reaction is supported on a honeycomb or the like. Since the temperature of the shift reaction is generally lower than the temperature of the reforming reaction, the gas flowing out of the reforming section 113 is cooled by the heat exchanger 114 to a temperature suitable for the shift reaction. Water for shift reaction is supplied to the high-temperature shift reaction unit 115 from the outside, but is not shown in order to avoid complication of the drawing.

The gas processed in the high-temperature shift reaction section 115 is further passed through a heat exchanger 116 to the low-temperature shift reaction section 11.
7 The low-temperature shift reaction unit 117 is also a unit for performing a shift reaction similarly to the high-temperature shift reaction unit 115, but the temperature suitable for the reaction is slightly lower than that of the high-temperature shift reaction unit 115. Therefore, the gas processed in the high-temperature shift reaction unit 115 is supplied to the heat exchanger 116 by the low-temperature shift reaction unit 11.
Cool to a temperature suitable for the reaction at 7.

The gas processed in the low-temperature shift reaction section 117 flows into the CO oxidation section 118. CO oxidation section 118
Is a unit for selectively oxidizing only carbon monoxide, and is a structure supporting a catalyst suitable for this reaction.
By the reaction in each unit described above, a hydrogen-rich fuel gas is generated from the raw material. Here, the structure of the sub-reforming unit 110 has been exemplified, but the other sub-reforming units 120 to 190 have the same configuration.

In the embodiment, the reforming section 113, the high-temperature shift reaction section 115, the low-temperature shift reaction section 117, the CO oxidation section 11
Although a case is described as an example, some of these may be omitted or an additional unit may be provided depending on the type of raw materials used for reforming.

FIG. 3 shows that the reforming unit 100 is
FIG. As described above, the sub-reforming units 110 to 190 have a square cross-sectional shape and are arranged in a grid. By arranging the sub-reforming units 110 to 190 so that the sides of the square are close to each other, each unit can be arranged without wasting space as compared with the case of a circular cross section or the like. Although not shown in FIG. 2, these sub-reforming units 110 to 190
Is entirely covered with a case 102. The sub-reforming units 110 to 190 are also provided with a space between the sub-reforming units 110 and 190.

These gaps function as a heat insulating mechanism for suppressing the transfer of heat between the sub-reforming units. These voids may be filled with a heat insulating material, but in this embodiment,
An air layer was used to suppress heat conduction between the sub-reforming units. The case 102 is hermetically sealed to prevent such air from leaking to the outside. In the embodiment, the nine sub-reforming units are independent. However, the entire sub-reforming unit may be integrally formed and the inside may be partitioned into nine units by a partition made of a heat insulating material.

As described above, the space between the case 102 and the sub-reforming units 110 to 190 is filled with the fuel cell 20.
Exhaust gas can be supplied. The exhaust gas is supplied from the fuel cell 20
Since the exhaust gas is heated in the case 102, the warm-up and temperature maintenance of each sub-reforming unit can be facilitated by introducing the exhaust gas into the case 102. As the supplied gas, various gases useful for warm-up and the like other than the exhaust of the fuel cell 20 can be applied. For example, a gas generated by the reforming unit 100, a combustion gas of the evaporator 15, a gas heated by a separately prepared heater, or the like can be used. A method may be adopted in which a heater or the like is provided in the gap and each sub-reforming unit is warmed up by the heat.

In the embodiment, the reforming section 113, the high-temperature shift reaction section 115, the low-temperature shift reaction section 117,
Oxidizing section 118 (hereinafter, these are collectively referred to as chemical reaction section)
, The amount of the catalyst, the temperature during the reaction, the pressure condition, the number of the sub-reforming units, and the like are set by the following method.

First, the maximum required hydrogen amount is set based on the maximum required output of the fuel cell 20. Next, a target value of the achievable space velocity SV is set. Generally, the gas processing capacity in the chemical reaction section is determined by the space velocity SV and the volume. The size of the unit can be reduced by selecting the type of catalyst and the reaction conditions so that a high space velocity SV is realized. Since the achievable space velocity SV is different for each of the reforming reaction, the shift reaction, and the selective oxidation reaction of CO, the target value is set in consideration of the balance between the three.

The reforming unit 100 is set so as to cover the previously set maximum value. Considering the maximum value of the required hydrogen amount and the space velocity SV, the total volume of the reforming unit 100 can be set.

On the other hand, when the space velocity SV is increased, there is a problem that the operating range is narrowed. In the present embodiment, a wide operating range is realized by switching the number of operating sub-reforming units. From this viewpoint, the number and volume of the sub-reforming units can be set in consideration of the operation range and the set space velocity SV. If the number of sub-reforming units is reduced, the amount of change in the amount of production due to switching of the number of operations increases, so when the required amount of hydrogen is small, waste of the raw material occurs or the reaction becomes unstable. there is a possibility. If the number of sub-reforming units is increased, the amount of hydrogen generated within the operating range can be switched in small increments. However, in this case, the control of the reaction of each sub-reforming unit may be complicated. In the present embodiment, nine sub-reforming units are provided in consideration of these factors.

According to the reforming unit of this embodiment configured as described above, by switching the operation number of the sub-reforming units, the efficiency of hydrogen in a wide range from a state where the required amount of hydrogen is relatively small to a maximum value is obtained. It is possible to generate hydrogen. Further, the heat capacity of the reforming unit 100 can be adjusted by switching the number of operating sub-reforming units. For example, during warm-up, the number of operating sub-reforming units is reduced so that
00 can be reduced, and the system can be warmed up.

B1. Modification Example (1) of Reforming Unit: In the embodiment, the case where the sub-reforming unit has a square cross section is illustrated (see FIG. 3). The cross section can take various shapes. FIG. 4 shows a reforming unit 100A as a first modification.
It is explanatory drawing which shows the cross-sectional shape of. In the modification, an example in which the cross section of the sub-reforming unit 110A is a regular hexagon has been described. As shown in the figure, eight sub-reforming units are arranged so that the sides of the regular hexagon are close to each other. A gap is provided between each sub-reforming unit. Thus, even if a regular hexagonal cross section is used, each unit can be arranged with relatively little space. Further, the regular hexagonal cross section has an advantage that the flow in each sub-reforming unit can be smoothed as compared with a square. This is because when the angle near the vertex of each sub-reforming unit (for example, region A in the drawing) becomes obtuse, the flow stagnation in this region can be suppressed.

FIG. 5 shows a reforming unit 1 as a second modification.
It is explanatory drawing which shows the cross-sectional shape of 00B. Here, the case where the cross-sectional shape of the sub-reforming unit 110B is a regular triangle is illustrated. Each sub-reforming unit is arranged so that sides of the equilateral triangle are close to each other. A gap is provided between each sub-reforming unit. Although the cross-sectional shape of the equilateral triangle is inferior in smoothing the flow in each sub-reforming unit, there is an advantage that the units can be arranged at a high density. That is, there is an advantage that the number of sub-reforming units per unit volume can be extremely increased.

FIG. 6 shows a reforming unit 1 as a third modification.
It is explanatory drawing which shows the cross-sectional shape of 00a. Each sub-reforming unit 110a is provided with the reforming unit 100 according to the first modification.
A (see FIG. 4) has a hexagonal cross section with rounded corners. By doing so, there is an advantage that the flow of gas at the corners (for example, the region A in the figure) can be smoothed without deteriorating the integration degree. Here, the case where the corners are rounded from the hexagonal cross section has been illustrated, but the present invention can be similarly applied to various cross sections such as a regular triangular cross section.

FIG. 7 shows a reforming unit 1 as a fourth modification.
It is explanatory drawing which shows the cross-sectional shape of 00C. Here, two types of sub-reforming units 110C and 111 having different sizes are used.
The case where C was used was exemplified. Sub-reforming unit 110,
Although the case where the cross section of 111C is a regular triangle has been illustrated, the shape is not limited to this. Further, the cross-sectional shapes of the large-sized sub-reforming unit 111C and the small-sized sub-reforming unit 110C may be different. Various sizes can be set for the sizes of the sub-reforming units 110C and 111C.
It is desirable to apply as 1C. In the third modification,
For example, while the central sub-reforming unit 111C is used in several stages, the operating status of the peripheral sub-reforming units 110C is flexibly controlled by controlling the operation status of the peripheral sub-reforming units 110C flexibly, especially when driving at high speeds or on hills when the demand for hydrogen is high. A method such as making the amount of hydrogen follow the required amount can be adopted.

A different sectional shape may be used in each chemical reaction section prepared in the sub-reforming unit. For example, as shown in the embodiment (see FIG. 2), the reforming section 113 may have a circular cross section, and each unit downstream of the heat exchanger 114 may have a polygonal cross section. In the embodiment (FIG. 2), the cross-sectional shapes of these units are unified to a square, but may be different. In this case, the realized space velocity S
It is preferable to select the shape of each unit so that the unit having a lower V has a larger sectional area. For example, in general, the space reaction SV that can be realized is lower in the shift reaction than in the reforming reaction. Therefore, it is preferable that the reforming section has a circular cross section and the high-temperature shift reaction section 115 and the like have a square cross section.
In this way, the difference in space velocity SV can be compensated to some extent by the volume of the unit.
It is possible to stabilize the reaction while reducing the size of 0.

B2. Modification of Modification Unit (2): FIG.
It is an explanatory view showing the composition of the sub-reforming unit as a 5th modification. Two sub-reforming units 110D, 120
The configuration for D has been exemplified. Each sub-reforming unit is C
Except for the O-oxidized portion 118D, each unit has the same configuration as that of the embodiment (see FIG. 2). From the upstream side, mixing sections 112D and 122D, reforming sections 113D and 123D,
Heat exchanger 114D, 124D, high temperature shift unit 115D,
125D, heat exchangers 116D and 126D, and low-temperature shift sections 117D and 127D
0D. CO oxidation part 118D
Is configured as a unit common to the sub-reforming units 110D and 120D. Therefore, the raw materials supplied to each of the sub-reforming units 110D and 120D are individually subjected to a reforming reaction and a shift reaction, and then the CO oxidation unit 1
At 18D, they are mixed and discharged from a single outlet. Here, the case where the CO oxidizing unit 118D is shared by two sub-reforming units has been described as an example, but the CO oxidizing unit 118D may be shared by three or more.

The CO oxidizing section 118D is a structure carrying a catalyst for selectively oxidizing carbon monoxide, as in the embodiment. A diffusion chamber 119D is provided in the CO oxidizing section 118D so that the supported catalyst can be used uniformly. The diffusion chamber 119D has orifices OR1, OR
2 and a sub-reforming unit 1
The gas that has flowed in from 10D and 120D is temporarily stored and acts to flow uniformly through the catalyst. Orifice OR1, O
The diameter of R2 is substantially uniform in the CO oxidizing unit 118D regardless of whether the reaction is performed in both of the sub-reforming units 110D and 120D or the case where the reaction is performed in only one of them. Is set to proceed.

As described above, by sharing the CO oxidizing section 118D with the sub-reforming units 110D and 120D,
Control of the selective oxidation treatment of carbon monoxide can be simplified. Generally, the selective oxidation treatment of carbon monoxide has a characteristic that the reaction can be performed at a very wide range of space velocity SV by controlling the temperature of the reaction section. In the fifth modification, the CO oxidizing unit 118D is connected to two sub-reforming units 110D and 110D.
By sharing 0D, the temperature control of the CO oxidizing unit 118D and the supply of oxygen necessary for the processing can be performed collectively, and the control during the reaction can be simplified.

In the fifth modified example, the case where only the CO oxidized portion is shared is exemplified, but sharing can be performed in various modes. For example, in addition to the CO oxidation unit, the low-temperature shift reaction unit may be shared. Sharing the low-temperature shift reaction section has the advantage of stabilizing the reaction. In general, in the low-temperature shift reaction, the achievable space velocity SV is relatively low, and it is necessary to secure a sufficient volume of the reaction section in order to stably process the generated carbon monoxide. If the low-temperature shift reaction unit is shared by a plurality of sub-reforming units, it is possible to sufficiently secure the volume of the low-temperature shift reaction unit. In particular, when the reaction is performed in only one of the sub-reforming units, the volume more than twice as easily as when the low-temperature shift reaction unit is provided for each sub-reforming unit can be easily achieved. It is possible to secure. Even in the case where the reaction is performed on both sides, considering the clearance and the space loss (see FIG. 4) due to the arrangement of the sub-reforming reaction section, etc.
A relatively large volume can be easily secured.
Therefore, the reaction can be stabilized while reducing the size of the entire reforming unit. Since the high-temperature shift section has a higher reaction rate than the low-temperature shift section, it may be provided separately for each sub-reforming unit. Of course, it may be shared like the low-temperature shift unit.

C. Reforming Control: FIG. 9 is a flowchart of the reforming control process in this embodiment. Control unit 10
Is a process that is periodically executed together with other control processes. When this processing is started, the control unit 10 switches the processing content depending on whether or not warming up is being performed (step S10). The term “during warm-up” refers to a state in which the temperature of the catalyst of the reforming unit 100 has not risen to a temperature suitable for the reaction.
The determination as to whether or not the engine is being warmed up can be made using parameters such as the temperature of the reforming unit 100, the elapsed time after starting the system, the concentration of hydrogen discharged from the reforming unit 100, and the like.

If the engine is being warmed up, a process for suppressing the heat capacity is executed (step S11). In the present embodiment, the heat capacity is suppressed by reducing the number of operating sub-reforming units 110 to 190. During warm-up, only some of the nine sub-reforming units are operated regardless of the required hydrogen amount. The operation number may be a fixed number set in advance, or may be varied according to the warm-up state of the reforming unit 100.

When the engine is not warming up, the number of operating sub-reforming units 110 to 190 is controlled according to the required amount of hydrogen. Therefore, the control unit 10 first inputs the required amount of hydrogen (step S12). The required amount of hydrogen is set based on a map or a function prepared in advance according to the required power of the fuel cell 20. Next, the sub-reforming unit to be operated and its output are determined based on the required hydrogen amount (step S13), and the valves 13, 14, 111-
191 is controlled to realize the determined operating state (step S14).

The sub-reforming units to be operated are set according to a prepared map. FIG. 10 is an explanatory diagram showing the relationship between the required hydrogen amount and the operation status of the sub-reforming unit. This corresponds to a mode of sequentially increasing the number of operations according to the required hydrogen amount. For convenience of explanation, an operation state in a case where four sub-reforming units having a triangular cross section shown in the upper part of the figure are provided is illustrated here. With the first unit as the center, the second to fourth units are arranged so as to surround the first unit.

The lower part of the figure shows the operation status of each sub-reforming unit according to the required hydrogen amount. In the section where the required hydrogen amount is a1 or less, only the first unit is operated, and the second to fourth units are stopped. In the section of a1 <required hydrogen amount ≦ a2, the second unit is further operated. Thereafter, similarly, as the required hydrogen amount increases, the third unit and the fourth unit are sequentially operated. The required hydrogen amounts a1, a2, a3, and a4, which are the boundaries between the sections, may be set based on the amount of hydrogen that can be generated by the sub-reforming unit.

Here, the case where a fixed sub-reforming unit is operated according to the required amount of hydrogen has been exemplified. A mode in which the operating sub-reforming units are periodically switched while maintaining the relationship between the required hydrogen amount and the number of operating units may be adopted. For example, in the control example of FIG. 10, in the section where a1 <required hydrogen amount ≦ a2, two sub-reforming units are operated. Therefore, while operating the first unit continuously,
No. 3, No. 4 and No. 4 may be operated periodically and sequentially. "No.1, No.2", "No.1, No.3", "No.1, No.4"
The three operating conditions are periodically realized. The reason why the first unit is continuously operated is that since this unit is located at the center, the operation easily contributes to the maintenance of the warm-up state of the second to fourth units. A mode in which the units operating including the first unit are periodically switched may be adopted.

By periodically switching the sub-reforming units that operate as described above, the warm-up state of each sub-reforming unit can be maintained relatively easily, and the responsiveness to fluctuations in the required hydrogen amount can be improved. can do. The switching cycle may be set as appropriate from the viewpoint of maintaining the warm-up state of the sub-reforming unit, may be a constant cycle, or may be changed according to the required hydrogen amount, the temperature of the sub-reforming unit, and the like. Is also good.

FIG. 10 shows an example in which the required hydrogen amount and the operation status are uniquely set, but the map may be switched between when the required hydrogen amount is increasing and when the required hydrogen amount is decreasing. . For example, consider a case where the required hydrogen amount is reduced to a3 or less when four sub-reforming units are operated with a3 <required hydrogen amount. According to the map of FIG. 10, the fourth unit is stopped according to the change in the required hydrogen amount. Instead, a map for reducing the required hydrogen amount may be prepared, and the first unit may be preferentially stopped. This is because the first unit is located at the center, and it is relatively easy to maintain a warm-up state by heat generated by the operation of the surrounding second to fourth units.

C1. Modification (1) of reforming control: Control of the number of operations can be realized in various modes. FIG. 11 is an explanatory diagram showing the relationship between the required hydrogen amount and the operation status of the sub-reforming unit as a first modification. The case where the output of each sub-reforming unit is controlled as well as the number of operating units in the same structure as the sub-reforming unit shown in FIG. 10 is illustrated.

As shown in the figure, the operation of each sub-reforming unit is controlled in three stages of outputs 0, 50, and 100%. An output of 50% means that the reaction takes place at 50% of the achievable space velocity SV. The output can be controlled by the amount of raw materials supplied to the sub-reforming unit and the reaction conditions.

In the modified example, in the section of the required hydrogen amount ≦ b1, the first unit is operated at 50% output. Units 2 to 4 stop. In the section of b1 <required hydrogen amount ≦ b2, the output of the first unit is increased to 100% while the second to fourth units are stopped. When the required hydrogen amount further increases, the second unit is operated at 50% output while the first unit is operated at 100%. Thus, the number of operations is increased in two stages of 50% output and 100% output according to the required hydrogen amount.

According to the control mode of the modified example, there is an advantage that the generated hydrogen amount can be changed in small steps. Also in the modified example, as in the embodiment (FIG. 10), the operating sub-reforming units may be periodically switched. The map may be switched between when the required hydrogen amount is increasing and when the required hydrogen amount is decreasing.

C2. Modification Example (2) of Reformation Control: FIG. 12 is an explanatory diagram showing the relationship between the required hydrogen amount and the operation status of the sub-reforming unit as a second modification example. The case where the output of each sub-reforming unit is controlled as well as the number of operating units in the same structure as the sub-reforming unit shown in FIG. 10 is illustrated.

In the first modified example, the mode in which the number of operating units is increased after all the outputs of the operating sub-reforming units have reached 100% has been described. In the second modified example, a mode in which the number of operating sub-reforming units is sequentially increased at a 50% output state, and then the output of each sub-reforming unit is sequentially increased is exemplified.

That is, as shown, the required hydrogen amount ≦ c1
In the section of No. 1, the first unit and the second unit are each operated at 50% output. The operation may be started from a state in which only the first unit is operated. Thereafter, as the required hydrogen amount increases, the third and fourth units are additionally operated at 50% output while the first and second units are maintained at 50% output. After all the units are operated at 50% output, the output of the first unit is increased to 100% in the section of c3 <required hydrogen amount ≦ c4 while maintaining the second to fourth units at the 50% output. . Thereafter, as the required hydrogen amount increases, the outputs of the second to fourth units are sequentially increased.

With this durability, as in the first modification, the amount of generated hydrogen can be changed little by little. Further, since the stop of each sub-reforming unit can be suppressed, there is an advantage that the warm-up state of the reforming unit can be easily maintained. Also in the second modified example, as in the embodiment (FIG. 10), the operating sub-reforming units may be periodically switched. The map may be switched between when the required hydrogen amount is increasing and when the required hydrogen amount is decreasing.

According to the hydrogen generation system of the embodiment described above, various advantages can be obtained by switching a plurality of sub-reforming units provided in parallel. First
Furthermore, by reducing the number of sub-reforming units that operate at the time of startup, the heat capacity of the entire reforming unit can be suppressed, and quick warm-up can be realized. Secondly, by switching the sub-reforming unit according to the required hydrogen amount after the start-up, it is possible to adjust the amount of hydrogen generated without greatly changing the space velocity SV of the sub-reforming unit.
Accordingly, it is possible to secure a wide operating range while achieving downsizing by the high space velocity SV. In addition, by using the control for periodically switching the operated sub-reforming units, the warm-up state of the reforming units can be relatively easily maintained, and the responsiveness to the fluctuation of the required hydrogen amount can be secured. It is also possible.

Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that various configurations can be adopted without departing from the spirit of the present invention. For example, the above-described control processing may be realized by software or by hardware. Further, in the embodiment, the combination of the hydrogen generation system and the fuel cell 20 is illustrated, but the hydrogen consumption system in applying the present invention does not need to be a fuel cell.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a fuel cell system as an embodiment.

FIG. 2 is a perspective view of the reforming unit 100.

FIG. 3 is a plan view of the reforming unit 100 as viewed from a mixing unit 112 side.

FIG. 4 is an explanatory diagram showing a cross-sectional shape of a reforming unit 100A as a first modification.

FIG. 5 is an explanatory diagram showing a cross-sectional shape of a reforming unit 100B as a second modification.

FIG. 6 is an explanatory diagram showing a cross-sectional shape of a reforming unit 100a as a third modification.

FIG. 7 is an explanatory diagram showing a cross-sectional shape of a reforming unit 100C as a fourth modification.

FIG. 8 is an explanatory diagram showing a configuration of a sub-reforming unit as a fifth modification.

FIG. 9 is a flowchart of a reforming control process in the embodiment.

FIG. 10 is an explanatory diagram showing a relationship between a required hydrogen amount and an operation state of a sub-reforming unit.

FIG. 11 is an explanatory diagram showing a relationship between a required hydrogen amount and an operation state of a sub-reforming unit as a first modified example.

FIG. 12 is an explanatory diagram showing a relationship between a required hydrogen amount and an operation state of a sub-reforming unit as a second modified example.

FIG. 13 is a perspective view showing a raw material reforming unit as a conventional technique.

[Explanation of symbols]

Reference Signs List 10 control unit 11 raw material tank 12 water tank 13, 14, 111 to 119 valve 15 evaporator 20 fuel cell 100, 100A, 100B, 100a, 100C reforming unit 102 case 110, 110A, 110B , 110a ... sub-reforming units 110C, 111C ... sub-reforming units 110D, 120D ... sub-reforming units 112, 112D, 122D ... mixing units 113, 113D, 123D ... reforming units 114, 114D, 124D ... heat exchangers 115 , 115D, 125D: High-temperature shift reaction section 116, 116D, 126D: Heat exchanger 117, 117D, 127D: Low-temperature shift section 118, 118D, 128D: CO oxidation section 119D: Diffusion chamber

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H01M 8/06 H01M 8/06 G (72) Inventor Takeshi Nishikawa 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Koichi Numata 1 Toyota Town, Toyota City, Aichi Prefecture F-term in Toyota Motor Co., Ltd. BA01 BA17 KK52 MM09 MM12

Claims (17)

[Claims] 1. A hydrogen generation system that generates a hydrogen-rich gas by a chemical reaction of a raw material, wherein a chemical reaction unit for the chemical reaction and at least one of a heat capacity and a volume of the chemical reaction unit are adjustable. A hydrogen generation system comprising: an adjustment mechanism; and a control unit that controls the adjustment mechanism according to an operation state required for the system. 2. The hydrogen generation system according to claim 1, wherein the operation state is a warm-up state of the system. 3. The hydrogen generation system according to claim 1, wherein the control unit performs the control according to a required amount of hydrogen. 4. The hydrogen generation system according to claim 1, wherein the chemical reaction unit includes, in at least a part thereof, a plurality of sub-chemical reaction units for performing the same chemical reaction in parallel. Is a hydrogen generation system that is a mechanism that can switch the number of operating sub-chemical reaction units used for the reaction. 5. The hydrogen generation system according to claim 4, wherein the control unit increases the number of operations with an increase in the required amount of the hydrogen. 6. The hydrogen generation system according to claim 5, wherein the control unit also controls an amount of a raw material supplied to each sub-chemical reaction unit according to a required amount of hydrogen. . 7. The hydrogen generation system according to claim 5, wherein the control unit controls a sub-chemical reaction unit used for the reaction while maintaining a relationship between the required amount of hydrogen and an operation number. A hydrogen generation system that switches at the right time. 8. The hydrogen generation system according to claim 4, wherein the sub-chemical reaction section has a polygonal cross section orthogonal to a gas flow direction, and the sub-chemical reaction sections are polygonal. Hydrogen generation system located close to the side of the. 9. The hydrogen generation system according to claim 8, wherein the sub-chemical reaction unit is a unit that performs a shift reaction for generating hydrogen from carbon monoxide and water. 10. The hydrogen generation system according to claim 4, wherein the chemical reaction unit comprises a multi-stage unit that performs a different chemical reaction, and a part of the multi-stage unit on the upstream side is the sub-chemical reaction unit. A hydrogen generation system configured as a shared reaction section, wherein the remaining portion on the downstream side is shared by a plurality of sub-chemical reaction sections. 11. The hydrogen generation system according to claim 10, wherein the chemical reaction unit performs at least a steam reforming or a partial oxidation reaction of the raw material, and a reforming unit generated by the reforming unit. A hydrogen generation system, comprising: a reformed gas processing unit that processes gas; at least the reforming unit is configured as the sub-chemical reaction unit. 12. The hydrogen generation system according to claim 10, wherein the shared reaction unit performs a shift reaction for generating hydrogen from carbon monoxide and water in the gas generated in the sub-chemical reaction unit. A hydrogen generation system including a shift reaction unit. 13. The hydrogen generation system according to claim 10, wherein the shared reaction unit includes an oxidation reaction unit that oxidizes carbon monoxide in the gas generated by the sub-chemical reaction unit. Generation system. 14. The hydrogen generation system according to claim 4, further comprising a heat insulating layer between the sub-chemical reaction units, for suppressing mutual heat transfer. 15. The hydrogen generation system according to claim 4, wherein a gap is provided between the sub-chemical reaction units. 16. The hydrogen generation system according to claim 15, further comprising a heat supply unit that supplies heat for heating the sub-chemical reaction unit to the gap. 17. A method for operating a hydrogen generation system that generates a hydrogen-rich gas by a chemical reaction of a raw material, wherein at least one of a heat capacity and a volume of a chemical reaction unit for the chemical reaction is generated during hydrogen generation. An operation method comprising a step of controlling according to an operation state required of the system.