JPH0647442B2 - Fuel reformer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel reformer that reforms a reforming raw material gas into a hydrogen-rich gas and supplies the reformed gas to a fuel cell.

[Conventional technology]

A fuel cell directly converts chemical energy into electric energy, and since it can obtain high thermal efficiency even with a small output, it has recently been developed and deployed as a mobile power source or a remote island power source that replaces the conventional engine generator and turbine generator. Is being promoted. By the way, as a hydrogen source of the fuel gas supplied to the fuel cell, methanol is used, which has a reaction temperature significantly lower than that of natural gas, LPG, or hydrocarbons which are the main components thereof, and which can be easily reformed. . These hydrocarbons and methanol are reformed into a hydrogen-rich gas by a steam reforming reaction under a reforming catalyst and become a fuel gas for a fuel cell.

By the way, the main component of natural gas, methane, is reformed by the following two reactions.

The reaction of CH ₄ + H ₂ O → CO + 3H ₂ (1) CO + H ₂ O → CO ₂ + H ₂ (2) (1) is an endothermic reaction carried out at 700 ℃ ~ 900 ℃ under Ni type reforming catalyst. The reaction (2) is an exothermic reaction carried out at 200 to 400 ° C under a Cu-based reforming catalyst. In addition,
The reaction (1) is carried out in a fuel reformer having a reaction tube filled with a Ni-based reforming catalyst, and the reaction (2) is carried out in a carbon monoxide shift converter containing a Cu-based reforming catalyst. Be seen.

On the other hand, as for methanol, the vaporized methanol gas is
It is believed to be reformed by the reaction of the stage.

CH ₃ OH → CO + 2H ₂ (3) CO + H ₂ O → CO ₂ + H ₂ (4) (3) and (4) are both performed at 200 ° C. under a Cu-based reforming catalyst.
The reaction (3) is an endothermic reaction, and the reaction (4) is an exothermic reaction, but in total, it is an endothermic reaction. The reactions (3) and (4) are performed only in the fuel reformer having a reaction tube filled with a Cu-based reforming catalyst because the reaction temperature is low and the concentration of carbon monoxide is low.

Since the steam reforming reaction in the reaction tube of the fuel reformer for reforming the reforming raw material gas such as methane or methanol is a large endothermic reaction, it is necessary to supply heat from the outside. The heat transfer from is rate limiting. The heat supply from the outside is performed by a high-temperature heat medium, for example, combustion gas, and the reaction tube is arranged in the casing of the fuel reformer, and the fuel gas is guided into the casing so that the reaction gas flows along the tube wall of the reaction tube. The reforming catalyst layer composed of the reforming catalyst in the reaction tube is heated to reform the reforming raw material gas into a hydrogen-rich gas by a steam reforming reaction.

As a device for steam reforming a reforming raw material gas as described above, a fuel reformer shown in FIG. 4 is conventionally known. In the figure, the fuel reformer 1 has a structure described below.
A furnace container 2 as a casing has a burner 3 as a heat medium supply source arranged on the upper part thereof, and a cylindrical partition wall 4 surrounding the burner 3 penetrates an end plate at the end of the furnace container 2. It is constructed by being suspended. Reference numeral 5 is a fuel supply pipe for supplying combustion fuel to the burner 3. The superheater tube 6 is a spiral tube and is arranged in the partition wall 4. An upper portion of the superheater tube 6 is provided with a reforming raw material gas inlet pipe 7 penetrating the end plate of the furnace vessel 2, while a lower portion thereof is provided with a portion of the reforming raw material gas. It is connected to the reactor 10 via a pipe 8. The reactor 10 is a concentric double reaction tube consisting of a reaction tube 12 in which an intermediate catalyst 11 is filled between an inner tube and an outer tube surrounding the partition wall 4, and a reaction tube 12a having a similar structure surrounding the reaction tube 12. A reformed gas manifold 13 having an outlet pipe 13a for collecting reformed gas from the reaction tubes 12 and 12a is provided in the upper part, and a header that communicates with each other and is connected to the lower part of each reaction tube is provided in the lower part.
14 is provided and configured, and is disposed in the heating chamber 9 defined by the partition wall 4 and the side wall of the furnace vessel 2. And reactor
A communication hole 15 is provided in the fuel cell 10, and the combustion gas can freely flow through the communication hole 15 inside and outside the reactor 10. A, B, and C are temperature measurement points of the reforming catalyst layer filled with the reforming catalyst layer 11, A is the lowermost portion of the reforming catalyst layer, B is the central portion, and C is the uppermost portion. It is a point. Reference numeral 16 is an exhaust pipe for exhausting combustion gas to the outside.

Next, a method of operating the fuel reformer having such a structure will be described. First, the fuel for fuel is supplied to the burner 3 through the fuel supply pipe 5, and the fuel is burned by the combustion air supplied to the burner 3 by the combustion air supply means (not shown). The combustion gas generated at this time flows down in the partition wall 4 to heat the superheat pipe 6, and then returns to the lower end of the partition wall 4 and rises in the heating chamber 9 to flow through the reaction tubes 12, 12a inside and outside thereof. After heating from the side surface, a part of the combustion gas is discharged to the outside from the discharge pipe 16 through the communication hole 15. Then, when the minimum temperature of the reforming catalyst layer in the reaction tubes 12, 12a becomes 100 ° C. or higher by the heating of the combustion gas, the reforming is started. That is, the reforming raw material gas is fed into the superheating pipe 6 from the reforming raw material gas inlet pipe 7. Then, the reforming raw material gas is heated by the combustion gas in the superheating pipe 6 to become a superheated gas, and this superheated gas flows into the reaction pipes 12 and 12a through the reforming raw material gas distribution pipe 8 and the inside of the reaction pipes 12 and 12a. Reforming catalyst
Under 11 is reformed to a hydrogen-rich gas. At this time, the reforming catalyst layer is controlled within a temperature range suitable for the reforming reaction. The reformed gas generated in the reaction tubes 12 and 12a is supplied to the external fuel cell as a fuel gas for the reaction gas from the outlet tube 13a through the reformed gas manifold 13.

[Problems to be Solved by the Invention]

When operating the fuel reformer as described above, the reforming catalyst layer in the reaction tube is heated by the high-temperature combustion gas as the heat medium, and if the minimum temperature of the reforming catalyst layer is 100 ° C or higher, the reforming raw material Is fed into the reaction tube to start reforming. Since the reforming reaction is an endothermic reaction as described above, the reforming reaction proceeds by heating the reforming catalyst layer with the combustion gas. However, if the amount of combustion gas is too small, the reforming catalyst becomes low temperature and unreformed gas is generated.If the amount of combustion gas is too large, the reforming catalyst deteriorates, and the catalyst poisons the electrode catalyst layer of the fuel cell. Since a reformed gas having a high concentration of carbon monoxide is generated, it is necessary to control the reforming catalyst layer within an appropriate temperature range, for example, in the range of 260 ° C to 300 ° C for a Cu-based catalyst.

However, when the reforming catalyst layers in the multiple reaction tubes 12, 12a are heated by the combustion gas, a temperature difference occurs in the reforming catalyst layers in the flowing direction of the combustion gas in each reaction tube, that is, in the vertical direction, and At the same level of the furnace vessel 2, a temperature difference occurs in the direction from the center to the outer periphery, that is, in the radial direction.

FIG. 5 is a graph showing the temperature rise characteristics of the fuel reformer when heating the reaction tubes 12 and 12a by the combustion gas from the burner 3 to cause the reforming reaction in the fuel reformer 1 of FIG. Where the abscissa represents the time elapsed from the start of heating of the reforming catalyst layer to the operation temperature range L within the proper temperature range of the reforming reaction, and the ordinate represents the temperature of the reforming catalyst layer. Measurement points A, B of the catalyst layer,
The temperature of C (see FIG. 4) is shown. The solid line shows the temperature of the reforming catalyst layer of the inner reaction tube 12, while the broken line shows the temperature of the reforming catalyst layer of the outer reaction tube 12a. From the figure, the temperature rising rate in the vertical direction of the reforming catalyst layer is highest in the lowermost part of the reforming catalyst layer together with the reaction tubes 12, 12a, and is lower in the order of the central part and the uppermost part. It is understood that the temperature rising rate of the reforming catalyst layer becomes slower from the upstream side to the downstream side.

On the other hand, regarding the temperature difference in the radial direction of the reforming catalyst layer, the temperature rising rate of the reforming catalyst layer in the reaction tube 12a on the outer peripheral side of the furnace vessel 2 is slower than the temperature rising rate of the reaction tube 12 on the central side. Be understood.

By the way, the minimum temperature of the reforming catalyst layer of the reaction tubes 12, 12a is 100
The starting time T until the reforming raw material gas can be fed into the reactor 10 at ℃ is further shortened by reducing the temperature difference in the vertical and radial directions of the reforming catalyst layer. Since the temperature of the reforming catalyst layer during the quality reaction reaches the proper range earlier and the reformed gas can be supplied to the fuel cell earlier, it is required to shorten the starting time.

It is an object of the present invention to reduce the temperature difference in the temperature distribution of the reforming catalyst layer so that the temperature rising rate distribution of the reactor can be made uniform and the start-up time at the time of reforming the reforming raw material gas can be shortened. To provide a fuel reformer equipped with a reactor.

[Means for Solving the Problems]

According to the present invention, a multi-reactor in which reaction tubes filled with a reforming catalyst are connected between an inner tube and an outer tube surrounding the inner tube and are concentrically and multiply arranged, The heating chamber defined by the casing and the casing inside the casing that penetrates the end plate of the casing is concentrically arranged to surround the casing, and the heat medium from the heat medium supply source flows into the casing. In the fuel reformer for heating the respective reaction tubes by flowing along the side surfaces of the respective reaction tubes in the heating chamber and reforming the reforming raw material gas flowing through the respective reaction tubes into a gas rich in hydrogen, The flow resistance of the heat medium in the passage of the heat medium flowing while heating each reaction tube is made smaller from the center of the casing toward the outer periphery.

More preferably, in the fuel reformer, a means for accelerating heat transfer is provided on the side surface of the reaction tube in contact with the heat medium from the upstream side to the downstream side where the heat medium flows.

[Action]

In the multiple reactor, the heat medium that heats each reaction tube flows along the side surface of each reaction tube, that is, the flow of the heat medium in the tube and the reaction tube, the adjacent reaction tubes and the path between the reaction tube and the casing. Since the resistance is reduced from the center of the casing toward the outer periphery, the heat medium flows in a larger amount in the passages on the outer periphery, so that the heat dissipation from the outer periphery is compensated for and the reforming catalyst phase in the radial direction of the multiple reactors is compensated. The temperature difference in the temperature distribution can be reduced. Further, a means for promoting heat transfer is provided on the side surface of the reaction tube in contact with the heat medium from the upstream side to the downstream side where the heat medium flows, for example, a fin for heat transfer is attached to the side wall from the upstream side to the downstream side. By increasing the area where heat transfer is performed, the temperature of the heat transfer medium gives heat to the reaction tube and decreases toward the downstream, but since the heat transfer area increases toward the downstream, the side surface of the reaction tube of the heat transfer medium Since the heat transfer to the heat medium becomes uniform, the temperature difference in the temperature distribution in the direction from the upstream side to the downstream side of the heat medium can be reduced.

〔Example〕

The most preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a fuel reformer according to an embodiment of the present invention. In FIG. 1, the same parts as those of the conventional example of FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. In the figure, in this embodiment, the reactor 10 is used as a multiple reactor
It is composed of 12,12a, 12b, 12c. One of the differences from the conventional example is that fins 20 are attached to the inner and outer surfaces of the reaction tubes 12, 12a, 12b, 12c as means for promoting heat transfer. As shown in the side development view of the reaction tube in FIG. 2, the fins 20 are attached in a narrower position from the upstream side to the downstream side where the combustion gas flows in the direction of arrow 21, and the heat transfer area is increased from the upstream side to the downstream side. Therefore, even if the temperature of the combustion gas decreases toward the downstream side, the amount of heat transfer becomes uniform and the reaction tube 1
The temperature difference in the vertical direction of the reforming catalyst layers in 2, 12a, 12b, 12c becomes small. The other one different from the conventional example is the partition wall 4 and the reaction tube 12, the reaction tubes 12 and 12a, the reaction tubes 12a and 12b, which are the passages through which the combustion gas flows along the side surfaces of the reaction tubes 12, 12a, 12b and 12c. The flow resistance of the combustion gas flowing in the passage of the combustion gas, which is a gap between the reaction tube 12b and the reaction tube 12c and between the reaction tube 12c and the side wall of the furnace vessel 2, is reduced in the above order. That is, in the figure, the gaps between the partition wall 4, the header 15 of each reaction tube and the side wall of the furnace vessel 2 are changed from the inside of the reformer 10 toward the outside by ΔG _1, ΔG.
_{When 3,} ΔG _{4 and} ΔG ₅ are set, this size is increased in this order, that is, ΔG ₁ <ΔG ₂ <ΔG ₃ <ΔG ₄ <ΔG
₅ , the combustion gas flows in a larger amount toward the passage on the outer peripheral side.

With such a structure of the reformer, the combustion gas from the burner 3 flows in the partition wall 4 and then the reaction tubes 12, 12a, 1 in the heating chamber 9
The combustion gas flows from the lower side to the upper side along the side surfaces of 2b and 12c, and the combustion gas heats each reaction tube. At this time, since the fins 20 are attached to each reaction tube so that the fins 20 are more closely connected from the upstream side to the downstream side where the combustion gas flows, the heat transfer amount is made uniform from the lower part to the upper part of the reaction tube, and the inside of the reaction tube is improved. The temperature difference in the temperature distribution in the vertical direction of the high quality catalyst layer becomes small. Further, since the flow resistance of the combustion gas passage is made smaller from the center of the casing toward the outer circumference, a larger amount of the combustion gas flows in the reaction tube closer to the outer circumference, and the reforming catalyst layer in each reaction tube of the large quantity reactor is The temperature difference in the radial temperature distribution is reduced.

FIG. 3 is a graph showing the temperature rise characteristics at the time of starting the fuel reformer according to this example. In the same manner as in FIG. 5, the horizontal axis represents the time elapsed from the start of heating of the reforming catalyst layer in the reaction tube. The ordinate indicates the temperatures at the measurement points A, B, and C of the reforming catalyst layer, while the abscissa and the ordinate scale and units are the same as those in FIG.
The solid line indicates the reforming catalyst layer in the innermost reaction tube of the reformer,
The broken line shows the temperatures at the measurement points A, B, C of the reforming catalyst layer in the outermost reaction tube of the reformer. From the figure, the temperature difference in the vertical and radial temperature distribution of the reforming catalyst layers in the reaction tubes arranged in multiple layers in the reformer is smaller than that of the conventional one, and the minimum temperature of the reforming catalyst layers is 100 ° C. It is understood that the startup time T up to is shorter than that of the conventional one.

Further, it is understood that the operating temperature range M during the reforming reaction becomes smaller than the conventional operating temperature range L shown in FIG. 5, which facilitates temperature control.

Although the burner is used as the heat medium supply source in this embodiment, the same effect can be obtained by using a heater such as a heat exchanger and using the heat medium from the heater.

In the above example, the case where the temperature difference in the temperature distribution in both the vertical direction and the radial direction of the reactor is reduced has been described, but in the case where only the radial direction may be reduced,
It is not necessary to change the density of the heat transfer promoting means in the vertical direction of the reactor, and the same density may be used.

〔The invention's effect〕

As is clear from the above description, according to the present invention, in a multiple reactor in which multiple reaction tubes are arranged, the flow resistance of the passage through which the heat medium for heating each reaction tube flows is measured from the radial center of the casing to the outer circumference. Since the heat medium flows in a larger amount in the passage on the outer peripheral side of the casing, the temperature difference in the temperature distribution in the radial direction of the reforming catalyst layers in the multiple reaction tubes can be reduced. Furthermore, by providing a means for promoting heat transfer on the side surface of the reaction tube in contact with the heat medium from the upstream side to the downstream side, the heat transfer of the heat medium to the side surface of the reaction tube becomes uniform. Therefore, it is possible to reduce the temperature difference in the temperature distribution in the direction from the upstream side to the downstream side of the heat medium. Therefore, by reducing the temperature difference in the temperature distribution in the flow direction and the radial direction of the heat medium, the startup time can be shortened, the life of the reforming catalyst can be extended, and the temperature control of the reforming catalyst layer can also be performed. As a result, the carbon monoxide concentration can be easily controlled to a predetermined value or less, and the power consumption at startup can be saved.

[Brief description of drawings]

FIG. 1 is a sectional view of a fuel reformer according to an embodiment of the present invention, FIG. 2 is a side development view of the reaction tube of FIG. 1, and FIG. 3 is activation of a reforming catalyst layer in the reaction tube of FIG. 4 is a cross-sectional view of a conventional fuel reformer, and FIG. 5 is a graph showing a temperature rise state at the time of starting the reforming catalyst layer in the reaction tube of FIG. . 1: Fuel reformer, 2: Furnace vessel, 3: Burner, 4: Partition wall, 10: Reactor, 11: Reforming catalyst, 12,12a, 12b, 12c
: Reaction tube, 20: Fin.

Claims (2)

[Claims] 1. A multi-reactor in which a reaction tube filled with a reforming catalyst is connected between an inner tube and an outer tube surrounding the inner tube so as to be concentrically and multiply arranged, Arranged concentrically around the cylinder in a heating chamber defined by the cylinder and the casing inside a casing that penetrates the end plate, and passed the heat medium from the heat medium supply source into the cylinder. In the fuel reformer that flows along the side surface of each reaction tube in the post-heating chamber to heat each reaction tube and reform the reforming raw material gas flowing through each reaction tube into a gas rich in hydrogen, A fuel reformer characterized in that the flow resistance of the heat medium in the passage of the heat medium flowing while heating the reaction tube is made smaller from the center of the casing toward the outer periphery. 2. The fuel reformer according to claim 1, wherein a means for promoting heat transfer is provided on the side surface of the reaction tube in contact with the heat medium as the heat medium flows from upstream to downstream. A fuel reformer characterized by the above.