JP3069743B2 - Two-stage catalytic combustion reformer for fuel cells - Google Patents

Description

The present invention relates to a two-stage catalytic combustion type reformer for a fuel cell, and has a simple structure suitable for ensuring uniform dispersion of the second-stage fuel. Regarding porcelain.

[Conventional technology]

The structure of the conventional two-stage catalytic combustion type reformer is 13A
This is shown in FIG. 13B.

In this reformer, the raw material hydrocarbon enters the reformer through the raw material inlet nozzle 1, first passes through the raw material header 2 occupying one end of the reformer, and stands up from a tube sheet that partitions the raw material header 2. It passes through a reforming catalyst layer 5 between an outer tube 3 and an inner tube 4 of a reaction tube composed of a double tube of a tube 3 and an inner tube 4, and generates a hydrogen-rich reformed gas by a reforming reaction. The generated reformed gas reverses the flow direction from the end of the outer tube 3 and passes through the inner tube 4 while recovering self-heat, and is taken out of the reformer from an outlet nozzle 7 provided at one end of the reformer.

The heat required for the reforming reaction is provided by the following two-stage catalytic combustion. That is, the fuel is divided into the first stage fuel and the second stage fuel, and the first stage fuel is mixed with the combustion air and enters the reformer through the inlet nozzle 8 provided at the other end of the reformer. The fuel is combusted in the first-stage combustion catalyst layer 10 provided on the upstream side of the fuel cell 8. The first-stage combustion gas thus burned gives heat to the reaction tube through the heat transfer particle layer 11 filled around the outer tube 3, and then, from the space around the outer tube 3 at an intermediate portion of the outer tube 3. Into the second stage premix zone 12.

On the other hand, the second-stage fuel passes through the connecting pipe 14 from the inlet nozzle 13 at one end of the reformer opposite to the inlet nozzle 8 of the first-stage fuel, and is provided in parallel between the outer pipes 3. Supply pipe
After passing through the fuel supply pipe 15, the fuel is jetted from the second-stage fuel nozzle 16 at the tip of the fuel supply pipe 15 to the premixing zone 12. The second-stage fuel flows from the premixing zone 12 toward one end of the reformer, burns around the outer tube 3 in the second-stage combustion catalyst layer 17, and further forms the second-stage transmission formed around the outer tube 3. Heat is applied to the reaction tube while passing through the hot particle layer 18 together with the first stage combustion gas, and then exits the reformer through a combustion gas outlet nozzle 19 provided at one end of the reformer.

[Problems to be solved by the invention]

The two-stage catalytic combustion type reformer according to the prior art described above does not sufficiently consider the simplification of the device structure and the dispersion of the second-stage fuel in the premix zone.

That is, as shown in the plan view of the 13B reaction tube / fuel supply tube, the number of fuel supply tubes 15 is one between the reaction tubes 3 arranged in a staggered manner.

For this reason, the fuel supply pipe 15 needs more than the number of the reaction pipes 3, so that the number of parts increases and the structure of the apparatus becomes complicated.

An object of the present invention is to simplify the structure of a two-stage catalytic combustion type reformer for a fuel cell and to ensure good mixing and dispersibility of the second-stage fuel with respect to the first-stage combustion gas flow.

[Means for solving the problem]

An object of the present invention is to provide a reformer that generates hydrogen supplied to a fuel cell by a steam reforming reaction of a hydrocarbon such as liquefied natural gas, and a first-stage catalyst that burns a first-stage fuel supplied from one end of a container. A combustion section, a second-stage catalytic combustion section provided with a space portion separated from the first-stage catalytic combustion section, and a forest that penetrates through the second-stage catalytic combustion section and reaches the inside of the second-stage catalytic combustion section. A double-tube type reaction tube containing a porous catalyst, and a fuel supply tube which is provided in parallel with the reaction tube and jets a second-stage fuel into the space in a direction perpendicular to the axis. Hydrogen is supplied, the exhaust gas of the fuel cell is supplied as the first-stage and second-stage fuel, and the hydrocarbon flowing through the outer tube of the double tube constituting the reaction tube is subjected to the first-stage and second-stage catalytic combustion. To the two-stage catalytic combustion reformer for fuel cells flowing in the opposite direction to the combustion gas As the arrangement of the reaction tube and the fuel supply tube, the reaction tubes are arranged in a staggered arrangement, reaction tubes having the same diameter as the fuel supply tube are arranged around the fuel supply tube at a pitch of 60 degrees, and The distance between the adjacent reaction tubes and the fuel supply tube and the distance between the closest reaction tubes were made equal, the fuel supply tube was placed at the center of the regular hexagon, and the reaction tubes were placed at each corner of the regular hexagon. This is achieved by a two-stage catalytic combustion type reformer for a fuel cell, wherein a plurality of pipe assemblies are arranged in a staggered manner.

The above object is also a reformer for generating hydrogen to be supplied to a fuel cell by a steam reforming reaction of a hydrocarbon such as liquefied natural gas, and the first stage for burning the first stage fuel supplied from one end side of the container. A catalytic combustion section, a second-stage catalytic combustion section provided with a space separated from the first-stage catalytic combustion section, and penetrating through the second-stage catalytic combustion section to reach the inside of the second-stage catalytic combustion section and stand. A double-tube type reaction tube containing a reforming catalyst, and a fuel supply tube provided in parallel with the reaction tube and ejecting a second-stage fuel to the space in a direction perpendicular to the axis. The hydrocarbon is supplied, the exhaust gas of the fuel cell is supplied as the first and second stage fuels, and the hydrocarbon flowing in the outer tube of the double tube constituting the reaction tube is the first and second stage catalyst. Two-stage catalytic combustion reforming for fuel cells flowing in the opposite direction to the combustion gas in the combustion section Angle in, as an array of the reaction tube and the fuel supply tube, the reaction tube was placed in a staggered arrangement, the reaction tube of the same pipe diameter as the fuel supply tube around the fuel supply pipe
Arrange at a 60 degree pitch, equalize the distance between adjacent reaction tubes and the fuel supply tube and the distance between the closest adjacent reaction tubes, arrange the fuel supply tube at the center of the regular hexagonal lattice, and arrange the reaction tubes. Outside the grid array arranged at each corner point of the regular hexagonal lattice, a pipe assembly in which the fuel supply pipe is arranged at the center of the regular hexagon and the reaction tube is arranged at each square point of the regular hexagon is arranged. This is achieved by a two-stage catalytic combustion type reformer for a fuel cell, wherein the reaction tube and the reaction tube in the tube assembly are partially overlapped.

In the arrangement of the reaction tubes and the fuel supply tubes, it is preferable that the distance between the closest reaction tubes is 1.1 to 1.3 times the outer diameter of the reaction tube.

It is preferable that the ejection speed of the second-stage fuel be 30 times or more the flow speed of the first-stage combustion gas flowing through the space.

[Action]

As an arrangement of the reaction tubes and the fuel supply tubes having the same tube diameter, when the reaction tubes are arranged at an equal distance around the fuel supply tubes at a pitch of 60 degrees, that is, the fuel supply tubes are arranged at the center of the regular hexagonal lattice. High-density and uniform arrangement is possible when a grid arrangement where reaction tubes are arranged at each corner, or a staggered arrangement of pipes where fuel supply tubes are arranged at the center of a regular hexagon and reaction tubes are arranged at each corner become.

In each of the above arrangements, the second-stage fuel is supplied from the fuel supply pipe to the closest reaction pipe by setting the ejection speed of the second-stage supply fuel to 30 times or more the flow rate of the first-stage fuel gas in the space. To a position about twice the distance of

〔Example〕

Hereinafter, a two-stage fuel reformer for a fuel cell according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall structural view of the embodiment.

In FIG. 1, raw material hydrocarbons extend from a raw material inlet nozzle 1 provided at a lower portion of a cylindrical container, through a raw material header 2 occupying a lower end portion of the container, and upward in parallel from a tube sheet partitioning the raw material header 2. A plurality of reaction tubes comprising a double tube of an outer tube 3 and an inner tube 4 pass through a reforming catalyst layer 5 filled between the outer tube 3 and the inner tube 4 and reform in a hydrogen-rich manner by a reforming reaction. Generates gas. The generated reformed gas reverses the flow direction from the obstruction at the upper end of the outer tube 3, descends while recovering the heat inside the inner tube 4, and flows from the connecting tube 20 connected to the inner tube 4 via the reformed gas header 6. From the container through a reformed gas outlet nozzle 7 provided at the lower end of the container.

The heat required for the reforming reaction is provided by catalytic combustion occurring in two stages. Exhaust gas from a fuel cell (not shown) to which hydrogen is supplied by the two-stage catalytic combustion reformer for a fuel cell is used as fuel for catalytic combustion. The fuel of this exhaust gas is divided into first-stage and second-stage fuels, and the first-stage fuel is combined with combustion air at the first-stage fuel /
The air enters the container through the air inlet nozzle 8 and the inlet nozzle 8
Are mixed by a premixer 9 provided downstream of the first stage, and then enter the first-stage combustion catalyst layer 10 and burn. Then, the first-stage combustion gas burned flows downward and gives heat to the reaction tube via the first-stage heat transfer particle layer 11 filled around the outer tube 3 at the upper part of the outer tube 3. In the middle part, it enters the second premixing zone 12 consisting of the space around the outer tube 3. Here, the first-stage combustion catalyst layer 10 and the first-stage heat transfer particle layer 11 constitute a first-stage catalytic combustion section.

On the other hand, the second-stage fuel flows from the second-stage fuel inlet nozzle 13 provided at the lower part of the container through the communication tube 14 to the second-stage fuel supply tube 15 extending upward between the outer tubes 3 in parallel with each other, A second-stage fuel nozzle 16 provided at the end of the second-stage fuel supply pipe 15 and located in the second-stage premixing zone 12 horizontally jets into the premixing zone 12, and mixes and diffuses with the first-stage combustion gas. The mixed gas of the second-stage fuel and the first-stage combustion gas is burned in the second-stage combustion catalyst layer 17 formed immediately below the premixing zone 12 to become the second-stage combustion gas. Heats the reaction tube while descending the second stage heat transfer particle layer 18 formed around the outer tube 3 at the lower portion of the outer tube 3 and then exits from the combustion gas outlet nozzle 19 provided at the lower portion of the container. . Here, the second-stage combustion catalyst layer 17 and the second-stage heat transfer particle layer 18 constitute a second-stage catalytic combustion section. The second stage fuel supply pipe 15
Has a double-pipe structure of an outer pipe and an inner pipe, and a space between the outer pipe and the inner pipe is filled with a heat insulating material such as a ceramic fiber.

First, in the two-stage catalytic combustion type reformer of the present embodiment, the first-stage combustion gas and the second-stage combustion gas flow in opposition to the flow of the process gas in the reforming catalyst layer formed in the reaction tube.

Next, the optimum arrangement of the reaction tube 3 and the fuel supply tube 15 will be described.

First, in the two-stage catalytic combustion type reformer of the present system, the first-stage combustion gas and the second-stage combustion gas flow in opposition to the flow of the process gas in the reaction tube. Therefore, an equilateral triangular lattice staggered arrangement is most suitable as the arrangement of the reaction tubes for increasing the combustion gas flow rate and improving the heat transfer.

On the other hand, the second-stage fuel is supplied from the supply nozzle 16 in a direction perpendicular to the combustion gas flow.

As a method of arranging the fuel supply pipe 15 for uniformly mixing and dispersing the second-stage fuel, according to the theoretical formula of the free jet and the result of the flow test performed based on this theory, the fuel supply pipes 3A to 3F
4th to 4th combinations of the three basic patterns shown in Fig. 3C
Various sequences shown in FIG. 11 were found to be optimal.

The basic pattern A shown in FIG. 3A is a system in which a fuel supply pipe 22 is placed at the center and six reaction tubes 21 are arranged in parallel at equal intervals at a pitch of 60 °, which is the basis of all the arrangement methods. .

The basic pattern B shown in FIG. 3B is a system in which one reaction tube 21 is placed at the center, and three fuel supply tubes 22 are arranged in parallel at equal intervals at 120 ° around it.

The basic pattern C shown in FIG.
One, ten, and ten pipes are arranged in a regular triangle in parallel, three at the vertices of the regular triangle are designated as fuel supply pipes 22, and the remaining seven
In this method, a book is used as a reaction tube 21.

As a method of arranging the reaction tubes and increasing the number of members, any one of the patterns A, B, and C is determined in the center, and the arrangement of the pattern A is extended around the center.

On the other hand, a reformer for a fuel cell is often operated in a state where both a reaction section in which a reforming reaction is performed and a combustion section for applying heat to the reaction section are pressurized. It is necessary to arrange the reaction tube and the fuel supply tube as close as possible to the circle.

In order to simplify the reformer structure and reduce the number of parts, it is optimal to use the basic pattern A alone or any of the arrangements 1 to 8 shown in FIGS.

In the arrangement 1 shown in FIG. 4, three basic patterns A are arranged so as to partially overlap each other around the basic pattern B.

Arrays 2 and 3 shown in FIGS. 5 and 6, respectively, are arranged such that six basic patterns A are partially overlapped around the basic pattern A.

The array 4 shown in FIG.
9 are partially overlapped and arranged.

The array 5 shown in FIG. 8 is one in which three basic patterns A3 are independently arranged.

The array 6 shown in FIG. 9 has six basic patterns independently arranged around the basic pattern A.

The array 7 shown in FIG. 10 is one in which three basic patterns A are partially overlapped and arranged, and six basic patterns A are independently arranged therearound.

The array 8 shown in FIG. 11 has three basic patterns A arranged around the basic pattern C.

In the arrangement, the arrangement 1 shown in each of FIGS.
A method of arranging the center lines of the tubes in an overlapping manner,
There are two methods of independently arranging the patterns without overlapping the center lines of the tubes as in arrangements 5 to 7 shown in FIG.

In the arrangements 1 to 4, one reaction tube can be heated from three directions, and the reaction tubes can be heated more uniformly than in the arrangements 5 to 7.

On the other hand, in the arrangements 1 to 4, the number of the fuel supply pipes is increased as compared with the arrangements 5 to 7 in comparison with the number of the reaction tubes, and the structure of the header portion is complicated.

In arrangements 5 to 7, one reaction tube cannot be heated evenly because the fuel supply tube is arranged with two reaction tubes in the arrangement. However, according to the flow test results and the theoretical formula of free jet, the combustion temperature due to the uniform dispersion of the second-stage fuel is sufficiently uniform, the structure of the second-stage fuel header can be simplified, and many reaction tubes are arranged per unit cross-sectional area. Has the advantages that can be.

In the theoretical formula of the free jet, the distance X required for completely mixing the second-stage fuel supplied at right angles to the first-stage combustion gas is represented by the following expression (1).

Where: w ₁ : First stage combustion gas flow rate w ₂ : Second stage fuel amount r ₁ : First stage combustion gas density r ₂ : Second stage fuel density v ₁ : First stage combustion gas flow rate v ₂ : Second stage fuel flow rate d _0: a nozzle orifice.

Further, the distance Y that is flowed by the first-stage combustion gas while the second-stage fuel advances by X is expressed by equation (2).

The molecular weight is 30-35 and the calorific value is 400-600kcal / m ³ N (LH
In the fuel cell reformer using V), in order to keep the distance of Y as short as possible, the injection speed of the second-stage fuel needs to be 30 times or more the flow velocity of the first-stage combustion gas. Further, in order to uniformly mix and disperse the second-stage fuel under these conditions, the interval between the second-stage fuel nozzles needs to be twice or less the reaction tube pitch.

FIGS. 2A and 2B show the estimated combustion temperature distribution of the second stage combustion section in the flow test based on the above operating conditions.

According to the flow test result performed by disposing the second stage fuel supply pipe at about twice the pitch of the reaction tubes, the estimated combustion temperature of the second stage became uniform near the average temperature. (See Figure 2B).

On the other hand, when the interval between the fuel supply pipes was four times the pitch of the reaction pipes, the estimated combustion temperature could not be kept uniform with respect to the average temperature. (See Figure 2A).

FIG. 12 shows an example of the set values of the flow rates of the second-stage fuel and the first-stage combustion gas for each load of the reformer.

The arrangement of the reaction tube and the fuel supply tube is as shown in FIGS. 3A to 3C to FIG. 11, but if it is necessary to further expand the reformer capacity, the arrangement 3, 3 shown in FIG. 4 to FIG. No.3 on the outer circumference of 4,5,6,7
This corresponds to a method of arranging patterns A shown in FIG.

〔The invention's effect〕

According to the present invention, in the two-stage catalytic combustion reformer for fuel, as the arrangement of the reaction tube and the fuel supply tube having the same tube diameter, the fuel supply tube is arranged at the center of the regular hexagonal lattice, and at each corner point. Use a grid arrangement to arrange the reaction tubes, or use a staggered arrangement of pipe assemblies in which the fuel supply pipes are arranged at the center of the hexagon and the reaction tubes are arranged at each corner, or an array of regular hexagonal lattices and tubes Using a combined arrangement, the center distance between adjacent fuel supply pipes and reaction tubes and the center distance between adjacent reaction pipes are set to 1.1 to 1.3 times the diameter of the reaction tubes, and the second stage supply fuel is injected. By setting the velocity to be at least 30 times the flow rate of the first stage combustion gas in the space, the second stage fuel reaches a position about twice as long as the distance from the fuel supply pipe to the nearest reaction pipe. The effects described in (1) are provided.

(1) The second-stage fuel from the fuel supply pipe can be uniformly dispersed around each reaction tube, and the mixing property with the first-stage combustion gas can be improved.

(2) The configuration of the fuel supply pipe and the reaction pipe of the second-stage catalytic combustion section can be simplified.

(3) The adaptability of the two-stage catalytic combustion reformer for fuel cells to scale-up can be improved by increasing the number of supply pipes and reaction tubes.

[Brief description of the drawings]

FIG. 1 is an overall structural view of a two-stage catalytic combustion type reformer for a fuel cell according to an embodiment of the present invention. FIGS. 2A and 2B are diagrams showing the mixing performance of a second-stage fuel by a gas flow test. 3A to 3C show the basic patterns of the reaction tube / fuel supply tube arrangement, FIGS. 4 to 11 show the arrangements 1 to 8 of the reaction tube / fuel supply tube, respectively, and FIG. FIG. 13A shows an example of the flow rate of the first-stage combustion gas and the ejection velocity of the second-stage fuel with respect to the load of the two-stage catalytic combustion type reformer. Figure 13B shows the reaction tube shown in Figure 13A.
It is an arrangement view of a fuel supply pipe. DESCRIPTION OF SYMBOLS 1 ... Material inlet nozzle, 2 ... Material header, 3 ... Outer tube (reaction tube), 4 ... Inner tube (reaction tube), 5 ... Reforming catalyst layer, 6 ... Reformed gas header, 7 ... reformed gas outlet nozzle, 8 ... first stage fuel / air inflow nozzle, 9 ... premixer, 10 ... first stage combustion catalyst layer, 11 ... first stage heat transfer particle layer, 12 ... second stage Eye premixing zone, 13 …… Second stage fuel inlet nozzle, 14 …… Communication tube, 15 …… Second stage fuel supply tube, 16…
… Second stage fuel supply nozzle, 17 …… Second stage combustion catalyst layer, 18
… Second heat transfer particle layer, 19… Combustion gas outlet nozzle, 20
…… A communication pipe.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C01B 3/38 H01M 8/06 B01J 8/06 301

Claims (4)

(57) [Claims] 1. A reformer for producing hydrogen supplied to a fuel cell by a steam reforming reaction of a hydrocarbon such as liquefied natural gas, wherein a first-stage fuel supplied from one end of a container is burned. A catalytic combustion section, a second-stage catalytic combustion section provided with a space separated from the first-stage catalytic combustion section, and penetrating through the second-stage catalytic combustion section to reach the inside of the second-stage catalytic combustion section and stand. A double-tube type reaction tube containing a reforming catalyst, and a fuel supply tube provided in parallel with the reaction tube and ejecting a second-stage fuel to the space in a direction perpendicular to the axis. The hydrocarbon is supplied, the exhaust gas of the fuel cell is supplied as the first and second stage fuels, and the hydrocarbon flowing in the outer tube of the double tube constituting the reaction tube is the first and second stage catalyst. A two-stage catalytic combustion reformer for fuel cells that flows in the opposite direction to the combustion gas in the combustion section As the arrangement of the reaction tube and the fuel supply tube, the reaction tubes are arranged in a staggered arrangement, reaction tubes having the same diameter as the fuel supply tube are arranged around the fuel supply tube at a pitch of 60 degrees, and The distance between the adjacent reaction tubes and the fuel supply tube and the distance between the closest reaction tubes were made equal, the fuel supply tube was placed at the center of the regular hexagon, and the reaction tubes were placed at each corner of the regular hexagon. A two-stage catalytic combustion type reformer for a fuel cell, wherein a plurality of pipe assemblies are arranged in a staggered manner. 2. A reformer for producing hydrogen supplied to a fuel cell by a steam reforming reaction of a hydrocarbon such as liquefied natural gas, wherein a first-stage fuel supplied from one end of a container is burned. A catalytic combustion section, a second-stage catalytic combustion section provided with a space separated from the first-stage catalytic combustion section, and penetrating through the second-stage catalytic combustion section to reach the inside of the second-stage catalytic combustion section and stand. A double-tube type reaction tube containing a reforming catalyst, and a fuel supply tube provided in parallel with the reaction tube and ejecting a second-stage fuel to the space in a direction perpendicular to the axis. The hydrocarbon is supplied, the exhaust gas of the fuel cell is supplied as the first and second stage fuels, and the hydrocarbon flowing in the outer tube of the double tube constituting the reaction tube is the first and second stage catalyst. A two-stage catalytic combustion reformer for fuel cells that flows in the opposite direction to the combustion gas in the combustion section As the arrangement of the reaction tube and the fuel supply tube, the reaction tubes are arranged in a staggered arrangement, reaction tubes having the same diameter as the fuel supply tube are arranged around the fuel supply tube at a pitch of 60 degrees, and Equalize the distance between the adjacent reaction tubes and the fuel supply tube and the distance between the closest adjacent reaction tubes, arrange the fuel supply tube at the center of the regular hexagonal lattice, and place the reaction tubes at each corner of the regular hexagonal lattice. Outside the arranged grid arrangement, a tube assembly in which the fuel supply pipe is arranged at the center of the regular hexagon and the reaction tubes are arranged at each corner point of the regular hexagon is arranged, and the reaction tubes in the lattice arrangement and the tube assembly in the tube assembly are arranged. A two-stage catalytic combustion type reformer for fuel cells, characterized in that the reaction tubes are partially overlapped. 3. An arrangement of said reaction tube and fuel supply tube,
Set the distance between the closest and adjacent reaction tubes to 1.1
The two-stage catalytic combustion type reformer for a fuel cell according to claim 1 or 2, wherein the ratio is set to 1.3 times. 4. The two-stage catalytic combustion type reforming for a fuel cell according to claim 3, wherein the injection speed of the second-stage fuel is 30 times or more the flow speed of the first-stage combustion gas flowing through the space. vessel.