Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Reaction chamber includes at least one perforated – porous,...
Reexamination Certificate
1998-05-15
2002-08-06
Johnson, Jerry D. (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Reaction chamber includes at least one perforated, porous,...
C422S211000, C422S198000, C048S127700, C431S007000, C431S170000, C431S326000
Reexamination Certificate
active
06428758
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a reformation reactor with a reaction zone in which a reformation catalyst is located and to which a gas mixture containing a hydrocarbon to be reformed can be supplied.
An area of application for reformation reactors that is becoming increasingly significant is motor vehicles operated by fuel cells. Reformation reactors of this type are used to obtain hydrogen from methanol supplied in liquid form in order to obtain the hydrogen required by the fuel cells. Depending on the processing conditions, the methanol can be converted by endothermal steam reformation, exothermal partial oxidation, or, for example, as an autothermal process by a combination of both reactions, into a reformate gas that is rich in hydrogen. For the sake of simplicity, in the present case the term “reformation” will also include the partial oxidation of methanol or another hydrocarbon that is used.
The liquid components that participate in the reformation reaction are evaporated before they enter the reaction zone. Usually this takes place either in a separate evaporator connected upstream of the reactor or in a heated reactor area spatially separated from, and connected upstream of, the reaction zone. The gas mixture components can be added to this evaporator area by ultrasonic atomization, for example. Another conventional method consists in the complete combustion of a liquid hydrocarbon and evaporation of the fuel or water added later by the hot combustion products. The problems with this conventional method consist primarily of the inexact monitoring of the evaporation process, which can lead to incomplete evaporation, in other words the formation of drops, pulsations, a high pressure drop, and high heat losses in the case of indirect heating as well as sluggish dynamics. These defects are not advantageous, for example, in the area of application to motor vehicles that operate by fuel cells. For reasons related to space requirements and because all the load changes typical of motor vehicle operation are rapid and frequent, a reactor type is desirable that has a compact design and reacts rapidly to load changes.
U.S. Pat. No. 3,798,005 discloses a reactor for producing a hydrogen-rich gas by catalytic oxidation, preferably of long-chain hydrocarbons such as C
6
H
14
and C
8
H
18
. The reactor consists of at least two sintered blocks located in series with a space between them, to which blocks a suitable catalyst material is added. At least the sintered block containing the catalyst and located first in the flow direction is designed for catalytic oxidation of the hydrocarbon, while at least the last sintered block in the flow direction is designed as a shift stage for converting carbon monoxide into carbon dioxide. Catalytic oxidation of the hydrocarbon typically takes place at relatively high temperatures between 900° C. and 1650° C. while the CO—CO
2
conversion reaction takes place at temperatures between approximately 150° C. and 500
0
° C. The water required for the CO—CO
2
conversion reaction is injected as steam into the space in front of each shift stage sintered block. In front of the first sintered block in the flow direction that contains the catalyst, there is a mixing chamber into which the hydrocarbon to be reacted is added through an injection line and an air stream is added through a catalyst-free sintered block on the inlet side. The quantity of oxygen in the air stream is adjusted so that the subsequent catalytic oxidation takes place as incomplete flame-free combustion. The air stream is supplied in a countercurrent on the outside of a reactor jacket and is preheated by the heat given off. A pipe complex located on the outlet side in the reactor and consequently subjected to the flow of reaction gas that is still hot is used to preheat the hydrocarbon to be reacted and the water that is injected.
Offenlegungsschrift DE 33 45 958 A1 discloses a methanol reformation reactor for producing hydrogen in a fuel-cell-operated motor vehicle and an operating method therefor in which a special starting phase is provided before subsequent continuous operation. In this starting phase, liquid methanol is burned in a combustion chamber of the reactor that is separate from a reformation reaction zone. The hot combustion gas flows through a combustion gas chamber that is in a heat-conducting connection through a heat-conducting wall with the reformation reaction zone and as a result indirectly heats the catalyst material located therein. In addition, the combustion gas, after passing through the combustion gas chamber, is recycled through the reformation reaction zone, thus also heating the catalyst directly. When the reaction zone has reached its operating temperature, in this manner, methanol combustion is terminated and a hot-gas valve is switched to remove the combustion gas from the system, while during continuous operation that then begins, a methanol/steam mixture is added to the reaction zone for steam reformation of the methanol. A burner that serves to maintain the heating of the reaction zone during continuous operation of the reactor is operated on the surplus hydrogen from the fuel cells.
A reformation reactor with a plate design is disclosed in Offenlegungsschrift JP 5-337358 (A) in which a distribution chamber is laminated to a combustion chamber with interposition of a fuel distributing plate. The distributing plate is provided with a large number of distributing openings. A fuel/air mixture is burned in the combustion chamber. The air is fed directly into the combustion chamber through a matching air feed line, while the fuel enters the distribution chamber through a matching fuel supply opening and travels from there through the openings in the distributing plate into the combustion chamber. In order to prevent backflow from the combustion chamber into the distributing chamber, a portion of the airflow can be supplied to the fuel feed line through a branch line with a controllable valve and premixed therein with the supplied fuel.
Patent DE 37 29 114 C2 discloses a catalytic oxidation reactor for ignitable gas mixtures, in which a gas-permeable first layer containing a suitable oxidation catalyst is contained in a reaction chamber connected with a cooling medium and provided on a side facing the supplied gas mixture with a gas-permeable second layer. On its side opposite the second layer, the first layer is covered by a third layer that is impermeable to gas and liquid and is in thermal contact with the cooling medium. The gas mixture to be reacted passes through the second layer into the first layer where the oxidation reaction takes place under the influence of the catalyst. The resultant reaction components, for example steam in the case of an oxygen/hydrogen conversion, are then brought out from the first layer in a countercurrent through the second layer and then discharged. The second, preferably porous, layer functions as a diffusion blocking layer that allows only a metered predetermined gas mixture quantity to reach the first layer and is composed of a material that is a poor conductor of heat so that heat removal takes place primarily through the third layer to the cooling medium.
The technical problem solved by the present invention is the provision of a reformation reactor and an operating method therefor for reforming a hydrocarbon-containing gas mixture that is especially suited for applications in which a compact reactor design and high reactor dynamics are required, especially for mobile applications, such as fuel-cell-operated motor vehicles. For the sake of simplicity, the term “hydrocarbon” will be used to refer to hydrocarbon derivatives as well, such as methanol.
The present invention achieves this goal by providing a reformation reactor comprising (1) a reaction zone in which a reformation catalyst is located and to which a hydrocarbon-containing gas mixture to be reformed can be supplied; and (2) an evaporator body that is flush and adjacent to reaction zone, wherein the evaporator bod
Megede Detlef Zur
Schuessler Martin
Doroshenk Alexa A.
Johnson Jerry D.
Xcellsis GmbH
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