JPH0429858Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a double tube reactor used in raw material gas reforming equipment for fuel cells, etc., and is particularly useful for preventing overheating of the cap at the tip of the reactor. The present invention relates to a double tube reactor having a suitable structure.

[Conventional technology]

The raw material gas reformer for fuel cells is required to be compact, highly efficient, and have high load following characteristics due to its usage requirements.In order to satisfy these requirements, two
Double-tube or triple-tube reformers have been developed.

FIG. 4 shows an overall structural diagram of a reformer having a double tube reactor according to the prior art.

The mixed gas of hydrocarbon and steam supplied from the raw material gas inlet nozzle 1 passes through the reforming catalyst layer 2 filled between the outer tube 12 and the inner tube 13 of the reactor,
During this time, it receives heat from the combustion section outside the outer tube 12, causing a reforming reaction and becoming H2 _- enriched reformed gas.

Further, a combustion catalyst layer 7 is provided in the combustion zone 20 of the reformer, and the fuel supplied from the fuel supply nozzle 5 and the air supplied from the air supply nozzle 6 are mixed in the premixing layer 14. After that, it burns in the combustion catalyst layer 7 and becomes a high-temperature gas of 1000° to 1200°C.
It enters the heat transfer zone 15 with the outer tube 12 and inner tube 13 of the reactor. Heat transfer particles 1 are placed in the heat transfer zone 15.
0 and transmits the heat of the high-temperature fuel gas to the outer tube 12.

FIG. 5 shows an enlarged view of the tip of the reactor in the prior art, and since this is the part with which the high temperature combustion gas generated in the combustion zone 20 first comes into contact, the tip cap of the reactor is Further, a reactor protection cap 9 is provided on the outside of the reactor 16,
The space formed by the tip cap 16 and the protective cap 9 is filled with a heat insulating material 19.
On the other hand, the reaction fluid passes through the reforming catalyst layer 2 filled between the outer tube 12 and the inner tube 13 from above to below,
After the reforming reaction has taken place, the catalyst passes through numerous holes provided in the catalyst receiver 18 and inside the tip cap 16.
It changes direction by 180 degrees and flows upward in the inner tube 13.

[The problem that the idea attempts to solve]

However, in the prior art reactor shown in FIG. 5, the fluid direction changing portion inside the tip cap 16 is a space that is not filled with reforming catalyst. The flow velocity of the reaction fluid that has passed through the space suddenly decreases in this space.
The reaction fluid changes direction by 180° and flows into the inner tube 13, but since most of the fluid flows through the shortest distance as shown by the streamline a, the flow line a drawn in the tip cap 16 is In the bottom space 21 where the reaction fluid is not filled, the reaction fluid stagnates or flows at an extremely slow flow rate, and the reaction fluid has a small film heat transfer coefficient and absorbs a small amount of heat, so the temperature in the bottom space 21 becomes high.

Because such a phenomenon is expected, the inner tube 13
Measures can be taken to increase the length and place the catalyst receiver 18 as low as possible, but during reactor operation, the inner tube 13 and the outer tube 12 have different tube wall temperatures, and the outer tube 12 has a higher temperature. , due to the large difference in thermal expansion,
Again, a space 21 is formed at the bottom of the tip cap, and when a portion of the interior with little heat absorption is exposed to the combustion gas, the temperature of this portion becomes extremely high. Therefore, in order to prevent high temperatures, the outer tube
A protective cap 9 is provided on the outer surface of the outer tube 12 and a heat insulating material 1 is provided in the space formed by the outer tube 12 and the protective cap 9.
However, since the protective cap 9 absorbs almost no heat from the inside and is only heated by the combustion gas, the tube wall temperature rises to near the temperature of the high-temperature combustion gas. .

The protective cap 9 is usually made of metal, but if it is deformed due to high-temperature oxidation or thermal distortion, and is used for a long time in a temperature change between high and low temperatures, it may break or fall off. There is.
Once the protective cap 9 is damaged, the insulation material 19
If the tip cap 16 falls off, the tip cap 16 will be directly exposed to the high-temperature combustion gas, and since the internal pressure will also be acting, this will lead to high-temperature creep rupture.

It is also possible to make the tip protection cap 9 from a non-metallic material with excellent heat resistance, such as ceramic material, but these materials have poor ductility and are susceptible to thermal shock caused by repeated rapid temperature increases and decreases. This does not essentially solve the problem, as there is a high possibility that it will get damaged.

The purpose of the present invention is to solve the problems of the prior art as described above and to provide a double-tube reactor with a structure that can prevent a local temperature rise at the bottom of the reactor tip cap. .

[Means to solve the problem]

The above objectives can be achieved by providing a reactant fluid flow guide on the inner surface of the reactor tip cap.

[Effect]

By providing a reaction fluid flow guide on the inner surface of the reactor tip cap, the reaction fluid is forced to pass over the entire surface along the inner surface of the tip cap at high speed, and the film heat transfer coefficient of this portion is reduced. Since the temperature becomes higher, it is possible to prevent a local temperature rise in the tip cap portion.

In this case, the important point is to what value the flow rate of the reaction fluid in the tip cap should be set; By setting the temperature slightly higher than that, a uniform temperature distribution can be obtained.

〔Example〕

Hereinafter, specific examples of the present invention will be explained using figures.

Embodiment 1 FIG. 1 is a schematic sectional view showing the structure of the tip of a reactor according to the present invention. A reactor tip cap 16 is attached to the tip of the reactor outer tube 12, and the tip cap 1
A tip flow guide 17 is provided fixedly inside the reactor inner tube 13, and a pipe 22 of a size that can be inserted into the inside of the reactor inner tube 13 is provided in the center of the tip flow guide 17. This indicates that the Here, the pipe 22 also plays the role of absorbing dimensional fluctuations caused by the temperature difference between the outer pipe 12 and the inner pipe 13 during the operation of the apparatus, and the length of the pipe 22 inserted into the inner pipe 13 is , it is necessary to make the length enough so that it will not come off from the inner tube 13 even if the above-mentioned dimensional fluctuation occurs. Further, a flat plate 23 is provided on the upper surface of the tip flow guide 17, and this serves as a catalyst receiver in the prior art, but it does not have holes as seen in the catalyst receiver in the prior art.
Grooves 25 are provided so that the reaction fluid flows into the outer circumference of the flat plate 23, as shown by streamlines.

FIG. 2 is a cross-sectional view taken along line A-A in FIG.
4 and a groove 25 are provided, and the groove 25 serves as a passage for the reaction fluid. In addition, the above protrusion 2
As shown in FIG. 1B, the height of the groove 4 gradually decreases at the bottom reaction fluid gathering part, and the height of the groove 4 becomes a groove 25, and the reaction fluid collected here flows as shown by the streamline b. It flows into the inner pipe 13 with a flow.

Here, by setting the area of the groove 25 so as to be equal to or slightly faster than the speed at which the reaction fluid passes through the reforming catalyst layer 2, the inner membrane heat transfer coefficient in the pipe can be adjusted. As a result of being able to efficiently absorb the amount of heat supplied from the external high temperature combustion gas, it is possible to prevent the occurrence of hot spots in the area.

Further, since the tip flow guide 17 is fixed inside the reactor tip cap 16, the dimension of the gap between the two does not change during operation of the apparatus.

In addition, the difference in dimensional fluctuation caused by the difference in thermal expansion between the outer tube 12 and the inner tube 13 can be reduced by the fact that a hole is provided in the center of the flat plate 23 of the flow guide 17 and that the pipe 22 is inserted into the inner tube 13. , since it is absorbed by sliding in this part, the outer tube 1
No stress is generated between the tube 2 and the inner tube 13. Here, in order to make the above slide possible, pipe 2
There is a gap between the outer surface of 2 and the inner surface of the inner tube 13, and the reaction fluid leaks through this gap.
This amount of leakage is predicted at the time of design, and the tip flow guide 1
By setting the dimensions of the 7 portions, it is possible to ensure that the cooling effect of the tip cap 16 portion is not substantially impaired.

Embodiment 2 Another embodiment of the present invention is shown in FIG. This is an example of using the reactor explained in Figure 1 with the reactor rotated 180 degrees vertically, and the reaction fluid is supplied from below, rises through the reforming catalyst layer 2, and reaches the tip.
The direction is changed by 180 degrees to flow into the inner tube 13, indicating that the structure is such that heating by high temperature combustion gas is applied from above the outside of the tip cap 16.

The major difference from the structure in Figure 1 is that the catalyst receiver 18
is fixedly provided at the tip of the inner tube 13, and the dotted line indicates the relative position of the catalyst receiver 18 with respect to the tip flow guide 17 at room temperature, and the solid line indicates the position at high temperature operation. In addition, the shape of the A'-A' section and the pipe 22
etc. are the same as in Figures 1 and 2.

The biggest difference when the reactor arrangement is rotated 180 degrees vertically is that in the structure shown in Figure 1, the reforming catalyst layer 2 is always in contact with the catalyst receiver due to its own weight;
In the case of this embodiment, even if the reforming catalyst layer 2 is initially filled up to the surface of the catalyst receiver 18, the packing density will gradually increase as the temperature is repeatedly raised and lowered by operating the device, and the packing density will increase accordingly. , C, a space is formed between the upper surface of the reforming catalyst layer 2 and the catalyst receiver 18.

As a means to deal with this phenomenon, the outer circumferential frame of the tip flow guide 17 is made longer than that shown in FIG. At the same time, consideration was given to minimizing the internal space volume of the tip cap 16 through which the reaction fluid flows, and the attachment part of the catalyst receiver 18 was welded and fixed to the inner tube 13 without providing a hole in the catalyst receiver 18 to allow the reaction fluid to flow. By forcing the flow along the inside of the tip cap 16, the same effect as in the structure of FIG. 1 can be obtained.

〔Effect of the invention〕

As mentioned above, in the double tube reactor used in raw material gas reforming equipment for fuel cells, etc.
The reactor tip cap has the structure of the present invention, that is, a reaction fluid flow guide is provided in the tip cap so that the reaction fluid is forced to flow along the inner surface of the tip cap;
This technology solves the problems of the conventional technology, eliminates the local temperature rise of the tip cap (occurrence of hot spots), and eliminates the need for the conventional tip protection cap. A tubular reactor could be provided.

[Brief explanation of drawings]

Figure 1 is a schematic sectional view showing the structure of the tip of the reactor according to the present invention, Figure 2 is a sectional view taken along line A-A in Figure 1,
Fig. 3 is a schematic sectional view showing the structure of another embodiment of the reactor tip portion according to the present invention, Fig. 4 is a sectional view showing the overall structure of a conventional raw material gas reformer, and Fig. 5 is a conventional type. FIG. 2 is a schematic cross-sectional view showing the structure of the tip portion of the reactor. 1... Raw gas inlet nozzle, 2... Reforming catalyst layer, 3... Reformed gas header, 4... Reformed gas outlet nozzle, 5... Fuel supply nozzle, 6... Air supply nozzle, 7... Combustion Catalyst layer, 8... Ceramic honeycomb, 9... Reactor protection cap, 10... Heat transfer particles, 11... Combustion gas outlet nozzle, 12...
Reactor outer tube, 13... Reactor inner tube, 14... Premixing layer, 15... Heat transfer zone, 16... Reactor tip cap, 17... Reaction fluid flow guide, 18...
...Catalyst receiver, 19...Insulating material, 20...Combustion zone, 21...Bottom space, 22...Pipe, 23...
... Flat plate, 24 ... Protrusion, 25 ... Groove.

Claims (1)

[Scope of utility model registration request] It consists of an inner tube and an outer tube, the gap between both tubes is filled with a catalyst, the end of the outer tube is covered with a tip cap, and the reaction fluid is allowed to flow through the catalyst layer into the inner tube while being heated from the outside. A double-tube reactor for carrying out a reaction, characterized in that a fluid flow guide for forcing a fluid to flow along the inner surface of the end cap is provided at the fluid folding part of the tip cap. vessel.