JP2001302208A - Reformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reformer hardly causing powdering and abrasion of a catalyst, having a large heat transfer area based on the amount of the catalyst, made without using an expensive material, capable of heating the catalyst to a prescribed temperature, small in pressure drop caused by a catalytic layer, and thereby capable of enabling the reformer to be extremely compacted and the cost to be reduced. SOLUTION: The catalytic layer 16 is produced by arranging plural reforming catalysts 11 having cylindrical shapes and through-holes in the axis directions, in series in the axis direction and an outer tube 12 has an inner diameter slightly larger than the outer diameter of the catalyst layer 16. The outer tube 12 is fixed at one terminal 12a, and extended in the axis direction so as to surround the catalytic layer 16 and so as to be longer than the catalytic layer, and closed at the other terminal 12b. The inner tube 14 has an outer diameter slightly smaller than that of the through-hole of the catalytic layer 16, is fixed at one terminal 14a, extended in the through-hole in the axis direction, and opened at the other terminal 14b present at this side of the other terminal 12b of the outer tube 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reformer for reforming hydrocarbons.

[0002]

2. Description of the Related Art Various types of reformers have been proposed as reformers that use hydrocarbon gas such as natural gas, LPG, naphtha, etc. as a raw material and reform this into a reformed gas containing hydrogen.

FIG. 3 shows a double-tube reformer disclosed in "Reformer" of Japanese Patent Application Laid-Open No. 60-264303. In this figure, reference numeral 1 denotes a reformer container, and 2 denotes a reforming tube having a circular cross section in which one end is sealed and a reforming catalyst layer 3 is provided between an inner tube and an outer tube. A plurality of the reforming tubes 2 are arranged in one phase of the vessel. Combustion air and fuel gas are introduced from the upper part of the vessel 1 and burned in the combustion chamber 4, and the high-temperature combustion gas is passed through the heat transfer packed bed 5 to heat the reforming tube 2 from the outer surface. On the other hand, the reforming catalyst layer 3
The raw material gas is introduced together with steam into the reforming catalyst layer, which is heated to be reformed into a reformed gas. The reformed gas is inverted at the top of the reforming tube 2 and descends through the inner tube. 3
Is heated to lower the temperature to be taken out.

FIG. 4 shows a double-tube reformer disclosed in "Reactor" of JP-A-2-31832. In this figure, a combustion gas 6 is introduced from the lower part of the container 1,
The reforming tube 2 is heated from the outside. On the other hand, a raw material gas is introduced into the reforming catalyst layer 3 together with water vapor from above, and is heated by the reforming catalyst layer to reform into a reformed gas. The heat is applied to the reforming catalyst layer 3 to lower the temperature and is taken out.

[0005]

As described above, in the conventional reformer, the reforming catalyst layer 3 is formed between the inner tube and the outer tube constituting the double tube. Is filled with a pellet or Raschig ring-shaped catalyst. But,
The conventional reformer has the following problems.

(1) Since the double pipe is heated by the high-temperature combustion gas, the catalyst is compressed and powdered in the double pipe due to thermal expansion / thermal shrinkage, and the catalyst changes in volume due to temperature change.
The catalysts in contact with each other are liable to wear. Therefore, conventionally, the radial thickness of the reforming catalyst layer is set to about five times the diameter of the catalyst particles to prevent the powdering and abrasion thereof. As a result, the diameter of the double tube is large (for example, 3 inches or more), and the heat transfer area of the double tube is small compared to the amount of catalyst, so that the apparatus becomes large and the cost increases.

(2) Due to the large thickness of the catalyst layer, to heat the inside of the catalyst to a predetermined reforming temperature (for example, about 750 ° C.), heat the outer surface of the double tube to a high temperature (for example, 900 ° C. or more). Need to be done. Therefore, it is necessary to use an expensive heat-resistant material (for example, Inconel) for the outer tube of the double tube, or to partially apply a ceramic coating.

(3) Since the reforming catalyst layer 3 is randomly filled with a pellet-shaped or Raschig-ring-shaped catalyst, the flow path area between the catalysts is not uniform, and the flow velocity between the narrow portion and the wide portion is small. Changes drastically, resulting in a large pressure loss.

The present invention has been made to solve the above problems. That is, the object of the present invention is:
The catalyst is less likely to be powdered and worn, the heat transfer area with respect to the amount of catalyst can be increased, the catalyst can be heated to a predetermined temperature without using expensive materials, and the pressure loss of the catalyst layer is small. And to provide a reformer capable of reducing costs.

[0010]

According to the present invention, a double tube (20) containing a catalyst layer (16) is provided between an outer tube (12) and an inner tube (14). In a reformer that heats the outer surface of a double tube, supplies a raw material gas containing steam between the outer tube and the inner tube, reforms the catalyst layer, and exchanges the reformed gas with the catalyst layer through the inner tube. The catalyst layer (16)
A plurality of reforming catalysts (11) having a cylindrical outer diameter and having a through hole in the axial direction are arranged in series in the axial direction,
The outer tube (12) has an inner diameter that is slightly larger than the outer diameter of the catalyst layer, one end (12a) is fixed, extends longer than the catalyst layer in the axial direction surrounding the catalyst layer, and the other end (12b). Is closed, the inner tube (14) has an outer diameter slightly smaller than the through hole of the catalyst layer, one end (14a) is fixed, extends in the through hole in the axial direction, and the other end (14b). Is opened before the other end (12b) of the outer tube.

According to the structure of the present invention, the inner diameter of the outer tube (12) constituting the double tube (20), which is the reforming chamber, is slightly larger than the outer diameter of the catalyst. Is
Only one reforming catalyst (11) enters in the radial direction. Therefore, the heat transfer area of the outer tube (12) surrounding the reforming catalyst can be relatively increased, and the heat transfer area per unit catalyst amount can be extremely increased.

Further, since the reforming catalysts (11) are regularly arranged in a line in the axial direction in the outer tube, the change in the flow velocity is small and the pressure loss when passing through the catalyst layer can be reduced. Further, since the outer surface and the inner surface of the reforming catalyst have a small gap with the outer tube (12) and the inner tube (14), the outer tube (1
Even if 2) and the inner tube (14) thermally expand / shrink, the catalyst is not compressed, and the catalyst does not wear or powder due to a temperature change.

Furthermore, the gap between the reforming catalyst (11) and the tube on both the inner and outer surfaces can be extremely small (for example, about 1 mm or less), so that the gas flow rate can be increased and the catalyst and the tube are in direct contact. Despite the absence, the heat transfer resistance of the tube wall can be reduced. Further, since the thin tube is inserted into the hollow portion of the catalyst and the reformed gas is passed therethrough, the sensible heat of the reformed gas can be used for the reforming reaction. Therefore,
Since the heat transfer area per volume of the reforming chamber can be extremely large, the reformer becomes compact, and the heat transfer resistance is small and the tube wall temperature can be reduced. Can be made of an inexpensive heat-resistant material (for example, heat-resistant stainless steel), and the cost can be reduced.

According to a preferred embodiment of the present invention, the first tube plate (22) to which one end (12a) of the outer tube (12) is fixed, and one end (14a) of the inner tube (14) are connected. It has a fixed second tube sheet (23), a raw material gas containing water vapor is supplied between the first tube sheet and the second tube sheet, and the reformed gas is taken out from the outside of the second tube sheet. With this configuration, the raw material can be easily supplied to each of the plurality of double tubes (20), and the reformed gas can be taken out.

The reforming catalyst (11) is preferably a hollow cylindrical Raschig ring. With this configuration, the heat transfer area per unit catalyst amount can be further increased as compared with the case where a reforming catalyst having a plurality of holes is used.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the same reference numerals are used for common parts in each drawing. FIG. 1 is an overall configuration diagram of the reforming apparatus of the present invention. As shown in this figure, the reformer 10 of the present invention has a plurality of double tubes 20 containing a catalyst layer 16 between an outer tube 12 and an inner tube 14,
0 is heated with a high-temperature gas, and a raw material gas containing water vapor is supplied between the outer tube 12 and the inner tube 14 to reform the catalyst layer 16. The heat is exchanged for heat recovery.

FIG. 2 is a configuration diagram of the reforming tube (double tube 20) of FIG. 1 and 2, the catalyst layer 1 of the present invention
Reference numeral 6 denotes a plurality of reforming catalysts 11 having a cylindrical outer diameter and having through holes in the axial direction, which are arranged in series in the axial direction. The reforming catalyst 11 is preferably a hollow cylindrical Raschig ring so as to increase the heat transfer area per unit catalyst amount, but is a cylindrical catalyst having a plurality of (for example, four) through holes. Is also good. The catalyst is preferably nickel oxide supported on alumina or calcium aluminate. The size of the catalyst is, for example, about 17 mm in outer diameter,
Use an inner diameter of about 6 mm and a length of about 17 mm.

The outer tube 12 has an inner diameter slightly larger than the outer diameter of the catalyst layer 16. This gap (the outer tube 12 and the catalyst layer 1
6) is set to a range where the heat transfer resistance can be reduced and the pressure loss is small without being affected by the thermal expansion / contraction of the outer tube 12. This gap is preferably set to, for example, 1 mm or less. One end 12a of the outer tube 12 is fixed to the first tube sheet 22,
It extends longer than the catalyst layer in the axial direction surrounding the catalyst layer 16, and the other end 12b is closed. With this configuration, the outer tube 12 can be freely thermally expanded.

The inner tube 14 has an outer diameter slightly smaller than the through hole of the catalyst layer 16. This gap (gap between the inner tube 14 and the catalyst layer 16) is set to a range where the heat transfer resistance can be reduced and the pressure loss is small without being affected by the thermal expansion / thermal shrinkage of the inner tube 14. This gap is also preferably set to, for example, 1 mm or less. One end 14a of the inner tube 14 is fixed to the second tube sheet 23, extends in the through hole in the axial direction, and the other end 14b is opened short of the other end 12b of the outer tube. With this configuration, the inner tube 14 can be freely thermally expanded.

In this example, a raw material gas containing water vapor is supplied between the first tube sheet 22 and the second tube sheet 23, and the reformed gas is taken out from the outside of the second tube sheet 23. Further, a high-temperature gas flows outside the double tube 20 to heat the catalyst layer 16 from the outer surface of the outer tube 12. This exhaust gas is discharged outside at an upper portion of the first tube sheet 22. Double tube 2
As the high-temperature gas for heating 0, a combustion gas can be used as in the related art. This high-temperature gas (combustion gas) is introduced from the outside in the example shown in the figure, but may be generated by burning fuel inside.

A mixture of a hydrocarbon such as natural gas, LPG, gasoline, naphtha, and kerosene and water is used as the raw material gas. Further, the heating chamber formed between the reformer container 1 and the double pipe 20 is configured to surround the reforming pipe (double pipe 20), and a heating fluid such as a high-temperature combustion gas flows, The heat required for the reforming reaction is supplied to the reforming chamber. Further, as disclosed in the conventional example, the heating chamber may be filled with a heat transfer promoting material (for example, a ceramic ball or the like).

As described above, according to the present invention, a reforming catalyst is regularly charged, and a plurality of hollow cylindrical catalysts are regularly arranged in the same concentric shape in a tube constituting a reforming chamber. Furthermore, a thin tube is inserted into the hollow portion of the catalyst so that the reformed gas can flow out through the inside of the thin tube. Since the inner diameter of the tube constituting the reforming chamber is slightly larger than the outer diameter of the catalyst, only one catalyst enters the tube in the radial direction, and the area of the tube wall surrounding the catalyst is small. This is the maximum, and the heat transfer area per reforming chamber can be extremely large.

Further, since the catalyst is regularly arranged in a line in the axial direction in the tube, the resistance of the fluid passing through the catalyst layer is reduced, the pressure loss can be reduced, and the catalyst may be worn due to a temperature change. Absent. In addition, since the gap between the catalyst and the inner and outer surfaces of the tube can be extremely small (for example, about 1 mm or less), the gas flow rate can be increased, and the heat transfer resistance of the tube wall can be reduced. Further, by inserting a thin tube into the hollow portion of the catalyst and letting the reformed gas pass therethrough, the sensible heat of the reformed gas can be used for the reforming reaction. As described above, since the heat transfer area per reforming chamber volume can be made extremely large, the reformer becomes compact, and even when the reforming temperature is about 750 ° C., the tube wall temperature can be reduced to about 810 ° C. Thus, the cost can be reduced by using heat-resistant stainless steel or the like as a material constituting the pipe and the reformer.

According to the structure of the present invention described above, a relatively large hollow cylindrical catalyst (for example, an outer diameter of 17 mm, an inner diameter (hollow diameter) of 6 mm,
Hydrogen production capacity of several NM
It can be easily applied to a small reformer for a fuel cell having a power generation capacity of less than ³ h ^-1 or less than several kW.

It should be noted that the present invention is not limited to the above-described embodiments and examples, and it is needless to say that various changes can be made without departing from the spirit of the present invention.

[0026]

As described above, the reformer of the present invention is
The catalyst is less likely to be powdered and worn, the heat transfer area with respect to the amount of catalyst can be increased, the catalyst can be heated to a predetermined temperature without using expensive materials, and the pressure loss of the catalyst layer is small. And an excellent effect that cost can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a reformer of the present invention.

FIG. 2 is a configuration diagram of a reforming tube of FIG. 1;

FIG. 3 is a configuration diagram of a conventional double-tube reformer.

FIG. 4 is another configuration diagram of a conventional double tube reformer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Reformer container, 2 reforming pipes, 3 reforming catalyst layers, 4 combustion chambers, 5 heat transfer packed layers, 6 combustion gases, 10 reformers, 11 reforming catalysts, 12 outer tubes, 12a one end, 12
b other end, 14 inner tube, 14a one end, 14b other end,
16 catalyst layer, 20 double tubes, 22 first tube sheet, 23
2nd tube sheet

Claims (3)

[Claims] 1. A double pipe (20) containing a catalyst layer (16) between an outer pipe (12) and an inner pipe (14). In a reformer in which a raw material gas containing water vapor is supplied between a pipe and an inner pipe to reform the catalyst layer, and the reformed gas exchanges heat with the catalyst layer through the inner pipe, A plurality of reforming catalysts (11) having a cylindrical shape and having through holes in the axial direction are arranged in series in the axial direction, and the outer tube (12) is slightly larger than the outer diameter of the catalyst layer. The inner tube (14) has an inner diameter, one end (12a) is fixed, extends axially longer than the catalyst layer around the catalyst layer, and the other end (12b) is closed. It has an outer diameter slightly smaller than the hole, one end (14a) is fixed, extends in the through hole in the axial direction, and the other end (14b) is other than the outer tube. End (12
A reformer, which is open just before b). 2. A first tube sheet (22) to which one end (12a) of the outer tube (12) is fixed, and a second tube sheet to which one end (14a) of the inner tube (14) is fixed. (23), wherein a raw material gas containing steam is supplied between the first tube sheet and the second tube sheet, and the reformed gas is taken out from the outside of the second tube sheet. The reformer according to any one of the preceding claims. 3. The method according to claim 1, wherein the reforming catalyst is a hollow cylindrical Raschig ring.
The reforming apparatus according to item 1.