JPH0450101A - Fuel reformer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel reformer that steam-reforms hydrocarbon-based raw fuel together with steam under a reforming catalyst to convert it into a hydrogen-containing gas.

[Conventional technology]

Reformed raw material gas, which is obtained by adding water vapor to hydrocarbon raw fuel such as natural gas or naphtha, is reformed into hydrogen-containing gas by heating with a heating medium under a reforming catalyst to generate reformed gas. A fuel reformer shown in FIG. 2 is known as a fuel reformer that supplies this reformed gas to a fuel cell via a carbon monoxide shift converter.

In FIG. 2, the fuel reformer 1 includes a reformer pipe 2 and a reformer pipe 2.
The furnace is comprised of a burner 3 disposed inside the furnace, and a furnace vessel 4 which is provided with the burner 3 at the top and surrounds from the outside a catalyst-filled portion in which the reforming tube 2 is filled with a reforming catalyst. In the reforming tube 2, 5 is an upright partition cylinder, and a cylindrical outer tube 6 and an inner tube 7 are arranged on both sides of the partition cylinder 5. The lower end of the outer tube 6 and the inner tube 7 is a partition cylinder 5
An outer annular space 8 and an inner annular space 9 are connected by a semi-torus-shaped bottom plate apart from the lower end thereof, and are connected at their lower ends by the outer tube 6 and the partition cylinder 5, and by the partition cylinder 5 and the inner tube 7, respectively.
is formed. A reforming catalyst 12 is filled in the lower half of the outer and inner annular spaces 8.9 to form an outer catalyst layer I.
O and the autocatalytic layer 11 are connected at a half-torus portion at the lower end.

The lower half of the partition cylinder 5 that partitions the autocatalyst layer 10 and the outer catalyst layer 11 has a heat insulating layer 13 that is thick from bottom to top. On the other hand, in the upper half of the outer and inner annular spaces 8°9, there are heat transfer particles 2 made of alumina etc. that promote convective heat transfer.
2 is filled to form a heat exchange section.

An inlet 16 for the reformed raw material gas is provided at the upper end of the outer annular space 8 via a reformed material gas manifold 15, and an inlet 16 for the reformed gas is provided at the upper end of the inner annular space 9 via a reformed gas outlet manifold 17. An outlet 18 is formed.

The burner 3 is provided inside the reforming tube 2, and the burner 3
The catalyst layer is arranged at the starting point and ending point level of the catalyst layer consisting of the outer catalyst layer 10 and the autocatalyst layer 11 so that the combustion gas from the reformer tube 2 heats the catalyst-filled portion in the reforming tube 2.

The furnace vessel 4 is equipped with a burner 3 in the upper part, and is provided so as to surround a catalyst layer consisting of an outer catalyst layer 10 and an autocatalyst layer 11 of the reforming tube 2 from the outside, and a fireproof heat insulating material is provided on the inner surface and bottom surface. 19
is installed. Inside the furnace vessel 4 is a combustion gas passage 20 in which combustion gas from the burner 3 flows along the inside of the reforming tube 2, turns around at the lower end of the reforming tube 2, and flows along the outside of the reforming tube 2. is formed. Note that the combustion gas passage 20 on the outside of the reforming tube 2 is filled with heat transfer particles 22 that promote convective heat transfer of the combustion gas.

In a fuel reformer having such a structure, when fuel is fed from the fuel port 23 to the burner 3 and combustion air is fed from an air inlet (not shown) to combust the fuel, the combustion gas from the burner 3 is combusted. Flows downward inside the reaction tube 2 which is the gas road 20, turns back at the lower end of the reaction tube 2, and flows upward through the combustion gas passage outside the reaction tube 2 filled with heat transfer particles 22,
The combustion gas is discharged from the combustion gas outlet 24 to the outside.

On the other hand, the reforming material gas consisting of raw fuel methane and water vapor flows in from the reforming material gas port 16, flows downward through the upper half of the outer annular space 8, and further flows downward through the outer catalyst layer 10 in the lower half. The gas is turned around at the lower end, flows upward through the autocatalyst layer 11 in the lower half of the inner annular space 9, and further flows through the upper half to flow outside from the reactant gas outlet.

As mentioned above, the outer catalyst layer 1 is heated by the combustion gas from the burner 3.
The catalyst layer consisting of 0 and autocatalyst layer 11 is heated, and the methane in the reforming raw material gas flowing through this catalyst layer in the opposite direction to the flow direction of the combustion gas is steam reformed by an endothermic reaction under the action of the reforming catalyst. The gas is reformed into reformed gas containing hydrogen. In this case, due to the endothermic reaction, there is a temperature difference between adjacent parts of the catalyst layer consisting of the outer catalyst layer 10 and the autocatalyst layer 11, and there is a temperature difference between the starting point where the reforming raw material gas enters and the reaction gas in the adjacent catalyst layer. The end point where the temperature difference is the largest is the partition cylinder 5.
Heat transfer is prevented by the heat insulating layer 13. Therefore, the temperature near the end of the catalyst layer is maintained at a high temperature necessary to complete the endothermic reaction, and a reformed gas that has been sufficiently reformed with steam can be obtained.

In addition, the high temperature gas coming out of the catalyst layer is transferred to the reformed raw material gas population 1 by the heat exchange section in the upper half of the outer and inner annular spaces 8.9.
6 and exchanges heat with the reformed raw material gas flowing through the upper half of the outer annular space 8.

In the above-mentioned fuel reformer, when raw fuel such as methane is steam reformed, the reforming reaction takes place at a high operating temperature, and the surface temperature of the heat-resistant steel that forms the reforming tube increases. , depending on the operating pressure, it can reach 700 to 900°C.

In addition, the above fuel reformer uses a carbon monoxide shift converter to convert the hydrogen-containing reformed gas obtained by this fuel reformer into a hydrogen-rich gas with a low carbon monoxide concentration. It is incorporated into a fuel cell power generation system that supplies the fuel as fuel to generate electricity using the fuel cell.

The starting and stopping time of such a fuel cell power generation system as a whole is desired to be shorter from the viewpoint of being a power generation device, and the target is about 1 to 4 hours. Furthermore, in the most frequent case, starting and stopping may be repeated every day. This means that the start-up time is about 10 to 100 times shorter than that for conventional chemical plants. The frequency of starting and stopping is about 250 times, and starting and stopping are performed under extremely harsh conditions.

[Problem to be solved by the invention]

As mentioned above, compared to conventional reformers for chemical plants, fuel reformers are frequently started and stopped under extremely harsh conditions, so temperature changes during startup and shutdown can cause
The metal material that makes up the reforming tube expands and contracts repeatedly, resulting in activation.

Stress is generated in the catalyst layer every time the catalyst is stopped, and in the worst case, the reforming catalyst may be crushed.Especially in the part A of the reforming tube 2 where the reforming raw material gas enters high, as shown in Fig. 2, and near the burner 3. As shown in Fig. 3, the temperature rise curve of part B is such that the reformer tube surface temperature P near the burner is equal to the reformer tube surface temperature Q at the catalyst bed inlet of the reforming raw material gas.
This results in a temperature distribution with a large temperature difference in the reforming tube. This temperature distribution also causes thermal deformation in the reforming tube and stress in the catalyst layer, leading to crushing.

By the way, if the catalyst were crushed and turned into powder, the pressure loss in the catalyst layer would increase, and in the worst case, there was a possibility that the fuel cell power generation system could not continue to operate.

For this reason, it is necessary for the catalyst particles themselves to have a certain degree of crushing strength, and increasing the crushing strength of the catalyst itself means increasing the strength of alumina, which is the carrier of the catalyst. To achieve this, there are two methods: increasing the firing temperature during carrier treatment or lengthening the treatment time, but in either case, γ-M, 03 can be replaced with α-M, 0. As a result of increasing the crystallinity, the pore volume inside the carrier decreases, resulting in a decrease in catalytic activity. This is because such pores directly contribute to the rate of catalytic reaction, and the larger the number, the better the catalytic activity.

As described above, since the relationship between catalyst strength and catalyst activity is contradictory, reforming catalysts for fuel reformers are manufactured with a certain degree of balance between strength and activity. For this reason, the amount of catalyst cannot be reduced, and for example, in the case of an on-site fuel cell power generation system, there is a drawback that the size of the fuel reformer cannot be reduced below a certain level.

The purpose of the present invention is to start the reforming catalyst in the catalyst layer in the reforming tube,
It is an object of the present invention to provide a fuel reformer that does not collapse when the temperature increases or decreases when the temperature is stopped.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, hydrocarbon raw fuel is passed together with steam through a reforming tube having a catalyst layer filled with a reforming catalyst, In fuel reformers that reform raw fuel into hydrogen-containing gas by heating, there is a flexible stress layer in the catalyst layer in the reforming tube that absorbs the stress of the reforming catalyst caused by thermal deformation of the reforming tube. The absorption layer is arranged in the length direction of the catalyst layer in the flow direction of the reformed raw material gas.

[Effect]

Start-up of a reforming tube having a catalyst layer consisting of a reforming catalyst.

Expansion/contraction and thermal deformation occur due to temperature changes and temperature distribution with large temperature differences that occur during shutdown, which causes stress in the reforming catalyst. At this time, if compressive stress is applied to the reforming catalyst, a flexible stress absorbing layer provided in the flow direction of the reformed gas within the catalyst layer will shrink in response to the applied stress, preventing the reforming catalyst from being crushed. Protect as such. Note that when the temperature change in the reforming tube or the temperature difference in the temperature distribution decreases, and the compressive stress applied to the catalyst layer decreases, the stress absorption layer increases its thickness again and has the effect of returning the catalyst layer to its original shape. do.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of a fuel reformer according to an embodiment of the present invention. In FIG. 1, parts that are the same as those in the conventional example shown in FIG. 2 are given the same reference numerals, and their explanations will be omitted. What is different from the conventional example in FIG.
A stress absorbing layer 30 made of a flexible material such as a ceramic fiber nonwoven fabric commonly used as a heat insulating material is attached to both sides of the structure.

This structure absorbs compressive stress that occurs in the reforming catalyst due to expansion, contraction, and thermal deformation of the reforming tube caused by temperature changes and temperature distribution of the reforming tube during startup and shutdown of the fuel reformer 1. to prevent crushing of the reforming catalyst.

Although this example describes a reforming tube with a double tube structure, even in a single tube structure, a flexible stress-absorbing layer can be placed in the catalyst layer in the length direction of the catalyst layer in the flow direction of the reforming raw material gas. The same effect can be obtained even if it is provided.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a flexible stress absorbing layer is disposed in the length direction of the catalyst layer in the flow direction of the reforming raw material gas in the catalyst layer consisting of the reforming catalyst in the reforming tube. With this structure, compressive stress generated in the reforming catalyst in the catalyst layer due to temperature changes and temperature distribution in the reforming tube when the fuel reformer starts and stops is absorbed by the flexible stress absorbing layer. It can prevent crushing of the reforming catalyst. Therefore, there are many pores that reduce the strength of the reforming catalyst, and therefore a catalyst with better activity can be used, so the amount of catalyst can be reduced, and the fuel reformer can therefore be made more compact.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a fuel reformer according to an embodiment of the present invention, Fig. 2 is a cross-sectional view of a conventional fuel reformer, and Fig. 3 is a temperature increase in the reforming tube when the fuel reformer is started. FIG. 3 is a diagram showing characteristics. 1: Fuel reformer, 2: Reforming tube, 3: Burner, 12: Reforming catalyst, 30: Stress absorption layer. Figure 2

Claims (1)

[Claims] 1) Hydrocarbon-based raw fuel is passed along with steam through a reforming tube that has a catalyst layer filled with a reforming catalyst, and the reforming tube is heated by a heat medium from a burner to convert the raw fuel into hydrogen-containing gas. In a fuel reformer for reforming gas to A fuel reformer characterized in that a catalyst layer is arranged in the length direction.