JPH1171101A - High pressure reformer - Google Patents

Abstract

(57) Abstract: Provided is a high-pressure reformer capable of obtaining high reforming efficiency under a high pressure of about 7 to 8 ata without increasing the operating temperature of a plate reformer. SOLUTION: A plurality of plate reformers 12a and 12b in which a plate-shaped reforming chamber Re and a heating chamber H are alternately stacked, and a combustion gas is provided outside the plate reformer and supplied to the heating chamber H. It has a combustor 14 and a hydrogen separator 16 for separating hydrogen from reformed gas containing hydrogen. The reforming chambers Re of the plurality of plate reformers are connected in series via a hydrogen separator 16, and supply the hydrogen gas 9 separated by the hydrogen separator through a bypass line 11 to the anode side of the fuel cell.
The hydrogen separation membrane 16a has a temperature of about 300 ° C. or more and a differential pressure of about 1 kg.
A palladium alloy film having a film thickness of 0.1 mm or more held at / cm ² or more is preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-pressure reformer for maintaining a high reforming rate under high pressure.

[0002]

2. Description of the Related Art Molten carbonate fuel cells have features not found in conventional power generation equipment, such as high efficiency and little impact on the environment, and are attracting attention as power generation systems following hydro, thermal and nuclear power. Are being researched and developed in various countries around the world. In particular, in a power generation facility using a molten carbonate fuel cell using natural gas as a fuel, a reformer is used to reform a source gas such as natural gas schematically shown in FIG. 4 into a gas containing hydrogen. . The reformer includes a combustion chamber Co and a reforming chamber Re separated by a partition wall.
(For example, anode exhaust gas from a fuel cell),
The reforming chamber Re is heated by the heat, and the raw material gas 2 flowing through the reforming chamber is reformed into a gas 4 containing hydrogen (hereinafter, referred to as a reformed gas) by the reforming catalyst 3 filled therein. Has become.

[0003] As such a reformer, a tubular type developed for a conventional plant has been developed as disclosed in
No. 35778, JP-B-5-9362, JP-A-62-2
No. 7303 has already been proposed for use in fuel cells.

On the other hand, a plate reformer having a configuration completely different from the above-mentioned conventional tubular reformer has already been proposed by the applicant of the present invention and is partially used. As illustrated in the principle diagram of FIG. 5, the plate reformer is configured such that the reforming chamber Re and the combustion chamber Co are each configured in a plate shape and are alternately stacked, and the combustion chamber Co includes particles. The combustion catalyst 5 is filled in a flat plate shape, and the fuel gas 1 and the combustion air 7 supplied from the external manifolds 6a and 6b flow as indicated by broken lines in FIG. ) And heat is generated, and the flue gas 8 is discharged to the external manifold 6 on the opposite side.
discharged from c. On the other hand, the reforming chamber Re is similarly filled with a particulate reforming catalyst 3 in a plate shape, and the raw material gas 2 supplied from the external manifold 6d flows as shown by a solid line in the drawing, and The raw material gas 2 is reformed by the action of
The reformed gas 4 is discharged from the external manifold 6e on the opposite side.

Further, the fuel chamber Co in FIG. 5 is replaced with a heating chamber H through which a high-temperature gas flows, and a separate combustion chamber (for example, a catalytic combustor) is used to supply high-temperature combustion exhaust gas to the heating chamber H. Other plate reformers have also been developed.
Compared with the tubular reformer, such a plate reformer has a large heat transfer area per volume and has a feature that it can be made very small and lightweight, and is not only used for fuel cells but also used in other fields (for example, hydrogen). Application).

[0006]

In the plate reformer described above, increasing the operating pressure is effective for improving plant efficiency and reducing the size. Therefore, the operating pressure of the plate reformer is adjusted to 7 to 8 atm in accordance with the operating pressure of the fuel cell.
It is desired to increase to about a. However, the reforming reaction of methane is CH ₄ + H ₂ O → 3H ₂ + CO. . Since the reaction is represented by the main reaction formula (Formula) and the number of moles (volume) increases by the reaction, the equilibrium constant decreases due to the increase in the pressure, and thus the reforming rate decreases. For example, at a pressure of 7 to 8 ata, the reforming rate becomes 80% or less, and the required reforming rate of 96% or more cannot be satisfied.

On the other hand, it is possible in principle to improve the reforming rate by increasing the reforming temperature. However, in a plate reformer, the upper limit of the reforming temperature is around 800 ° C. due to the temperature limitation of the partition walls. However, in order to raise the temperature further than this, it is necessary to use a heat-resistant material (for example, a ceramic material) that is very expensive and has poor workability, which is not practical.

The present invention has been made to solve such a problem. That is, an object of the present invention is to increase the operating temperature of the plate reformer to 7 to 8 ata.
It is an object of the present invention to provide a high-pressure reformer capable of obtaining a high reforming efficiency under a relatively high pressure.

[0009]

According to the present invention, a plurality of plate reformers in which a plate-shaped reforming chamber Re and a heating chamber H are alternately stacked, and a plate reformer installed outside the plate reformer are provided. A combustor for supplying combustion gas to the heating chamber H; and a hydrogen separator for separating hydrogen from reformed gas containing hydrogen, wherein the reformer chambers of the plurality of plate reformers are connected via a hydrogen separator. A bypass line that is connected in series, and further supplies hydrogen separated by the hydrogen separator to the anode line of the fuel cell, bypassing the downstream plate reformer,
A high-pressure reformer characterized by the above is provided.

[0010] According to this apparatus, the hydrogen in the reformed gas reformed in the upstream reformer is selectively separated by the hydrogen separation device arranged in the middle of the plurality of plate reformers. The hydrogen concentration decreases, and the methane reforming reaction (formula) is promoted in the downstream reformer. Therefore, even if the reforming rate in the uppermost stream reformer is reduced to, for example, about 80%,
In order to separate hydrogen, the reforming rate in the next reformer is also about 8
0% can be maintained, and 80 can be maintained by two reformers.
+ 20 × 0.8 = about 96% reforming rate can be achieved. Further, by arranging three or more units similarly in series, a higher reforming rate can be obtained.

According to the present invention, a plate reformer in which a flat heating chamber H, a reforming chamber Re, and a separation chamber Se are sequentially stacked, and the heating chamber installed outside the plate reformer. A high-pressure reforming apparatus is provided, comprising a combustor for supplying combustion gas to H, wherein the partition walls of the reforming chamber Re and the separation chamber Se are formed of a hydrogen separation membrane.
With this configuration, the reforming chamber Re and the separation chamber Se are formed by the hydrogen separation membrane.
Is formed, the hydrogen in the reformed gas reformed in the reforming chamber is selectively separated in situ through the hydrogen separation membrane, so that the hydrogen concentration decreases and the methane reforming in the reforming chamber is performed. The quality reaction is promoted, and even at a temperature of about 800 ° C., a reforming rate of 96% or more can be achieved with a single plate reformer without being limited by the equilibrium constant.

According to a preferred embodiment of the present invention, the hydrogen separation membrane is a palladium alloy membrane having a thickness of 0.1 mm or more and maintained at a temperature of about 300 ° C. or more and a differential pressure of about 1 kg / cm ² or more. With this configuration, 1 cm ³ / cm ²
min or more of hydrogen can be separated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common parts are denoted by the same reference numerals. FIG. 1 is a configuration diagram of a fuel cell power generation facility using a high-pressure reformer according to the present invention. In this figure, the high pressure reformer 10 of the present invention is shown.
Are a plurality of (two in this figure) plate reformers 12a and 12b in which a flat reforming chamber Re and a heating chamber H are alternately stacked.
And a combustor 14 installed outside the plate reformers 12a and 12b to supply the combustion gas 8 to the heating chamber H, and a hydrogen separator 16 for separating hydrogen from the reformed gas 4 containing hydrogen. .

A plurality (two) of plate reformers 12a, 1
The reforming chamber Re of 2b is connected in series via a hydrogen separator 16. The fuel cell further includes a bypass line 11 that supplies the hydrogen separated by the hydrogen separator 16 to the anode line of the fuel cell by bypassing the downstream plate reformer 12b.
The hydrogen gas 9 separated in 6 is supplied to the anode side of the fuel cell 20. Since the pressure of the separated hydrogen gas 9 is lower than that of the reformed gas 4 for hydrogen separation, the hydrogen gas 9 is supplied under pressure by the pressurizing pump 11a.

In FIG. 1, reference numerals 14a and 14b denote flow control valves for controlling the flow rate of the combustion gas 8, 21 denotes a desulfurizer,
22 is a fuel preheater, 23 is a turbine compressor, 24 is CO
_{2 is a} recycle blower, 25 is an air blower, and 20a is a control valve for the amount of circulating cathode gas.

When the fuel cell power generation equipment shown in FIG. 1 is operated at a high pressure of about 7 to 8 ata, according to this apparatus, the hydrogen separation unit disposed between the (two) plate reformers 12a and 12b is separated. Since the hydrogen in the reformed gas 4 reformed by the upstream reformer 12a is selectively separated by the device 16, the hydrogen concentration decreases, and the methane reforming reaction (formula (2)) is performed in the downstream reformer 12b. ) Is promoted. Therefore, even if the reforming rate in the reformer 12a on the most upstream side is reduced to, for example, about 80%, the reforming rate in the next reformer 12b may be maintained at about 80% in order to separate hydrogen. Thus, a reforming rate of 80 + 20 × 0.8 = about 96% can be achieved with two reformers. Further, by arranging three or more units similarly in series, a higher reforming rate can be obtained.

FIG. 2 is another configuration diagram of the high-pressure reformer of the present invention. In this figure, (A) is a plan view, and (B) is a cross-sectional view taken along line AA. The high-pressure reformer 10 of the present invention includes a flat heating chamber H, a reforming chamber Re, and a separation chamber S.
The plate reformer 12 includes a plate reformer 12 in which e is sequentially stacked, and a combustor 14 that is provided outside the plate reformer 12 and supplies the combustion gas 8 to the heating chamber H. The partition walls of the reforming chamber Re and the separation chamber Se are constituted by the hydrogen separation membrane 16a. Combustor 1
4 is the same as the fuel device in FIG.

That is, the high-pressure reforming apparatus shown in FIG. 2 is different from the high-pressure reforming apparatus in that the separation chamber Se having the hydrogen separation membrane 16a as a partition is in the plate reformer and is constituted by a single reformer. 1
And is the same in other respects.

With this configuration, the partition wall of the reforming chamber Re and the separation chamber Se is constituted by the hydrogen separation membrane 16a.
e, the hydrogen in the reformed gas 4 is selectively separated in situ through the hydrogen separation membrane 16a, so that the hydrogen concentration is reduced and the methane reforming reaction (formula) in the reforming chamber is promoted. Even at temperatures around 800 ° C., a reforming rate of 96% or more can be achieved with a single plate reformer without being limited by the equilibrium constant.

In this example, the separated hydrogen gas 9
Is lower than that of the reformed gas 4 for hydrogen separation. Therefore, it is preferable that the pressure be supplied to the anode side of the fuel cell by pressurizing with a pressure pump 11a (not shown).

FIG. 3 shows the principle of the hydrogen separation membrane. It is known that palladium and palladium alloy films have a property of selectively transmitting hydrogen. This hydrogen permeation mechanism is considered as follows. Hydrogen molecules are adsorbed on the palladium film. The adsorbed hydrogen molecules dissociate into hydrogen atoms. Since the reaction is an endothermic reaction, atomic hydrogen can be easily formed on the surface of the film when the film is heated or the raw material gas is heated and used. Hydrogen atoms are ionized and split into protons and electrons. Atomic hydrogen is a proton (proton) and an electron (electron), and since palladium lacks two electrons in the outermost shell, it can easily take off hydrogen electrons. Protons diffuse from the front surface of the palladium to the back surface.
For this movement, the hydrogen concentration (hydrogen partial pressure) on the front surface / source gas side must be higher than the hydrogen concentration (hydrogen partial pressure) on the back surface / purified hydrogen side. The protons that have reached the back surface recombine with the electrons on the palladium film surface to become hydrogen atoms. Hydrogen atoms combine to form hydrogen molecules. It is molecularly associated with the catalytic ability of the palladium film surface. Hydrogen molecules are desorbed from the pallet membrane. Hydrogen permeates through the above process.

Since only hydrogen which can be in a proton state permeates the palladium film in this way, other molecules which cannot be in such a state cannot permeate the palladium film. It is also called atomic sieves because hydrogen appears to be transmitted in atomic form. The hydrogen permeation rate of the palladium film changes depending on factors such as pressure, temperature, and film thickness. The permeation amount increases as the partial pressure difference increases, as the temperature increases, and as the film thickness decreases. For example, a temperature of about 300 ° C
As described above, a film thickness of 0.1 mm maintained at a differential pressure of about 1 kg / cm ² or more
By using the above barium alloy film, 1 cm ²
Per 1 cm ³ / min or more of hydrogen.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0024]

As described above, according to the high-pressure reformer of the present invention, high reforming efficiency can be obtained under a high pressure of about 7 to 8 ata without increasing the operating temperature of the plate reformer. , Etc. have excellent effects.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel cell power generation facility using the method of the present invention.

FIG. 2 is a configuration diagram of a high-pressure reformer of the present invention.

FIG. 3 is a principle view of a hydrogen separation membrane.

FIG. 4 is a schematic configuration diagram of a conventional reformer.

FIG. 5 is a principle diagram of a conventional plate reformer.

[Explanation of symbols]

Reference Signs List 1 fuel gas 2 raw material gas (process gas) 3 reforming catalyst 4 reforming gas 5 combustion catalyst 6a to 6e external manifold 7 combustion air 8 combustion gas 9 hydrogen gas 10 high pressure reformer 11 bypass line 11a pressurizing pump 12, 12a, 12b the plate reformer 14 combustor 16 hydrogen separator 16a hydrogen permeable membrane 20 fuel cell 21 desulfurizer 22 fuel preheater 23 turbine compressor 24 CO ₂ recycle blower 25 air blower

Claims (3)

[Claims] 1. A plurality of plate reformers in which a plate-shaped reforming chamber Re and a heating chamber H are alternately stacked, and a combustion gas is provided outside the plate reformer and supplied to the heating chamber H. A combustor, and a hydrogen separator for separating hydrogen from reformed gas containing hydrogen, wherein the reforming chambers of the plurality of plate reformers are connected in series via a hydrogen separator, and A high-pressure reformer, comprising: a bypass line for supplying hydrogen separated by the separator to a fuel cell anode line by bypassing a downstream plate reformer. 2. A plate reformer in which a flat heating chamber H, a reforming chamber Re, and a separation chamber Se are sequentially stacked, and a combustion gas is provided outside the plate reformer to the heating chamber H. A reforming chamber Re and a separation chamber Se.
A high-pressure reforming device, wherein the partition wall is formed of a hydrogen separation membrane. 3. The hydrogen separation membrane is a palladium alloy membrane having a thickness of 0.1 mm or more and maintained at a temperature of about 300 ° C. or more and a differential pressure of about 1 kg / cm ² or more. 3. The high-pressure reformer according to 2.