Modifying device

Details Modifying device Modifying device

2001-08-28

2004-11-09

Stoner, Kiley (Department: 1725)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Including heat exchanger for reaction chamber or reactants...

C422S198000, C422S218000

Reexamination Certificate

active

06814944

ABSTRACT:

TECHNICAL FIELD
This invention relates to a shift conversion unit for causing reformed gas, which has been produced by reforming hydrocarbon-based feed gas by partial oxidation reaction, to undergo shift conversion by water gas shift reaction with catalyst.
BACKGROUND ART
In general, hydrogen can be produced by reforming hydrocarbon or methanol. Fuel reforming units for producing hydrogen through such reforming can be used for fuel cells, hydrogen engines or the like.
As a reforming unit of such kind, there is conventionally known one which is incorporated into a fuel cell system as disclosed in Japanese Unexamined Patent Publication No. 11-67256. This fuel reforming unit includes a fuel reformer loaded with catalyst which exhibits activity to partial oxidation reaction, and is designed to introduce feed gas into the fuel reformer to produce reformed gas with hydrogen by partial oxidation reaction of the feed gas.
Further, in order to reduce CO (carbon monoxide) in the reformed gas produced in the above manner and improve the yield of hydrogen, the reformed gas is generally caused to undergo shift conversion by subjecting it to water gas shift reaction with shift conversion catalyst in a shift reaction section of a shift conversion unit.
Specifically, in the water gas shift reaction, carbon monoxide is oxidized by water to convert into carbon dioxide and hydrogen as expressed in the following chemical formula.
CO+H
2
O→CO
2
+H
2
Meanwhile, for the shift conversion unit of this kind, its shift reaction section has poor heat resistance and therefore cannot receive the reformed gas as supplied at high temperature (for example, 700° C.) from its reforming reaction section and cause such high-temperature reformed gas to undergo reaction. Accordingly, the unit is designed to divide the shift reaction section into high-temperature and low-temperature shift reaction sections, first introduce the reformed gas from the reforming reaction section into the high-temperature shift reaction section after decreasing its temperature down to for example 400° C. and then introduce the reformed gas having exited from the high-temperature shift reaction section into the low-temperature shift reaction section after further decreasing its temperature down to for example 200° C.
In this case, however, there is the need for controlling respective inlet temperatures of the reformed gas flowing into the high-temperature and low-temperature shift reaction sections. This creates the problem of complicating the component layout for satisfying the need.
Further, under the temperature conditions where the reaction speed is high as in the above case, the reaction cannot be realized. Therefore, the above unit cannot avoid that the temperature range within which the reformed gas can undergo shift conversion is limited narrowly.
Furthermore, in the water gas shift reaction under the high temperature conditions, it is necessary to increase the amount of catalyst in order to ensure the heat resistance of the catalyst. This correspondingly increases the thermal capacity of the shift reaction section thereby causing the problem of deteriorating its response to load variations and start-up characteristics.
The present invention has been made in view of these problems and therefore an object thereof is to enable the high-temperature reformed gas from the reforming reaction section to undergo shift reaction in the shift reaction section just as it stands by contriving the construction of the shift conversion unit and to thereby simplify the construction of the shift conversion unit.
DISCLOSURE OF INVENTION
To attain the above object, in the present invention, the shift reaction section of the shift conversion unit subjects the reformed gas from the reforming reaction section to shift reaction while heat-exchanging it with feed gas or heat recovery gas toward the reforming reaction section.
More specifically, the present invention is directed to a shift conversion unit having a shift reaction section (
10
) for causing hydrogen-rich reformed gas produced by reaction including partial oxidation of feed gas in a reforming reaction section (
6
) to undergo shift conversion by water gas shift reaction with shift conversion catalyst. In this shift conversion unit, the shift reaction section (
10
) is arranged to introduce the reformed gas from the reforming reaction section (
6
) directly into a reformed gas passage (
11
) and effect the shift reaction while heat-exchanging the reformed gas with the feed gas.
Thus, the high-temperature reformed gas from the reforming reaction section (
6
) is introduced directly into the shift reaction section (
10
) and in the shift reaction section (
10
), the reformed gas is then caused to undergo shift conversion by water gas shift reaction while undergoing heat exchange with the feed gas in the feed gas passage (
3
) which should be supplied to the reforming reaction section (
6
). Accordingly, the reformed gas having exited from the reforming reaction section (
6
) will undergo shift conversion while keeping its high temperature. Therefore, the reformed gas can undergo shift conversion over a wide temperature range from high temperature conditions where the reaction speed is high to low temperature conditions where the reaction speed is low but the gas reacts advantageously at equilibrium.
Further, the need to control the temperature of the reformed gas can be eliminated, thereby simplifying the construction of the shift conversion unit.
Furthermore, the loading amount of the shift conversion catalyst into the shift reaction section (
10
) can be decreased and the thermal capacity can be reduced correspondingly. As a result, the shift reaction section (
10
) can maintain excellent response to load variations and start-up characteristics.
The shift conversion catalyst of the shift reaction section (
10
) is preferably noble metal catalyst with heat resistance or catalyst in which Pt, Pt alloy or Ru alloy is used as active metal. This provides desirable shift conversion catalyst for effecting shift reaction at the high temperature. In other words, if the noble metal catalyst with heat resistance is used, the catalyst can exhibit excellent endurance and hold high activity over a wide temperature range. Alternatively, if the catalyst in which Pt, Pt alloy or Ru alloy is used as active metal is employed, the catalyst can exhibit high activity at high temperatures and makes it difficult to cause methanation.
The shift conversion catalyst of the shift reaction section (
10
) can be applied to or supported on porous material. Since the porous material has a large surface area, the use of this material can increase the contact area between the shift conversion catalyst and the reformed gas in the shift reaction section (
10
) to increase the reaction rate and improve the efficiency of heat radiation.
The porous material is preferably of either foam metal, cordierite or ceramics. In this case, there can be obtained desirable porous material especially for ensuring the increase in the contact area of the catalyst with the reformed gas.
In the vicinity of the shift reaction section (
10
), a feed gas passage (
3
) can be provided for supplying the feed gas to the reforming reaction section (
6
). With this arrangement, the feed gas in the feed gas passage (
3
) located in the vicinity of the shift reaction section (
6
) is heated by heat of reaction in the shift reaction section (
10
). Accordingly, the heat of reaction in the shift reaction section (
10
) can be recovered for the preheating of the feed gas and this self-recovery of heat can improve the thermal efficiency of the shift conversion unit.
In the above case, the shift reaction section (
10
) and the feed gas passage (
3
) can be integrally formed in a housing (
1
). With this arrangement, the construction of the shift conversion unit can be simplified, thereby providing cost reduction.
A heat exchanger (
15
) may be provided for exchanging heat of reaction and sensible heat in the shift reaction section (
10
) with heat

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