Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
2000-03-30
2002-06-11
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C429S010000, C429S010000, C429S010000, C429S006000, C429S006000
Reexamination Certificate
active
06403243
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel cell system having a fuel cell which has a supply line and a discharge line for a fuel as well as a supply line and a discharge line for an oxidizing agent. Such a system also has a fuel tank for a fuel comprising hydrocarbons, which is connected to a filter element for preventing the release of hydrocarbons. Furthermore, the invention concerns a method of regenerating the filter element in a fuel cell system.
2. Discussion of the Prior Art
Fuel cells are already known and have gained considerably in significance in recent years, in particular in the area of the automotive industry.
In a way similar to battery systems, fuel cells generate electrical energy by chemical means, the individual reactants being continuously supplied and the reaction product being continuously removed. In this case, the fuel cells are based on the operating principle that electrically neutral molecules or atoms bond with one another and thereby exchange electrons. This process is referred to as the redox process. In a fuel cell, the oxidation and reduction processes are physically separated. The electrons given off during the reduction can be conducted as a current through a load, for example the electric motor of an automobile.
Used as gaseous reaction partners for the fuel cell are, for example, hydrogen as the fuel (anode gas) and oxygen (cathode gas) as the oxidizing agent. If it is desired to operate the fuel cells with a fuel which is readily available and easy to store, such as natural gas or methanol, the hydrocarbon must initially be converted into an oxygen-rich gas by reforming.
When filling a fuel tank with a fuel which comprises hydrocarbons and subsequently converting it into the fuel for the fuel cell, for instance by steam reforming or the like, as well as when venting the fuel tank, hydrocarbons are released in an unwanted manner. Since the hydrocarbons are harmful to the environment and, what is more, can also cause damage in the fuel cell system, they must be bound in a suitable way. This generally takes place by means of a filter element, for example an active carbon filter, as is known for fuel tanks of vehicles with internal combustion engines, for example from WO 97/33765. This filter element must be regenerated from time to time in order to ensure its serviceability. If regeneration does not take place in time, the hydrocarbons can pass through the filter element and into the atmosphere unhindered.
Similarly, hydrocarbons can also get into the atmosphere as a result of gas leaks in the tank system (cf. for example German reference DE 19818697 A).
However, legislation prescribes, for example for Germany in the form of the 21st Bundes-Immissionsschutzverordnung [German federal regulation on air pollution control] of Oct. 7, 1992, that no or only a very small amount of hydrocarbons may get into the atmosphere.
German reference DE 691 26 321 T2 (European reference EP 0559816 B) discloses a power generating system which includes, inter alia, a fuel cell system of the generic type which is provided with devices for supplying and removing fuel and oxidizing agent. Furthermore, this fuel cell system is equipped with a cleaning device for the removal of hydrocarbons. Although the cleaning device is connected to the fuel tank via a line, it does not serve for cleaning the flow of exhaust gas but for cleaning the fuel which is supplied to the fuel cell.
SUMMARY OF THE INVENTION
Setting out from this cited prior art, the present invention is therefore based on the object of improving a fuel cell system of the type mentioned above so that the that the disadvantages described are avoided. In particular, it is intended to provide a fuel cell system in which the filter element can be regenerated in a simple and reliable way. Finally, an improved method of regenerating a filter element is also to be provided.
Pursuant to these objects, and others which will become apparent hereafter, one aspect of the present invention resides in a fuel cell system in which a filter element is connected to the discharge line for the oxidizing agent and/or the discharge line for the fuel.
The fuel cell system according to the invention firstly allows the filter element to be regenerated in a simple and low-cost way. For this purpose, the flow of exhaust gas of the oxidizing agent (cathode gas) and/or the fuel (anode gas) is passed through the filter element. As a result, the filter element is regenerated by the flow of exhaust gas passed through it entraining the hydrocarbon molecules. After leaving the filter element, these molecules can then be burned, for example in a device described in more detail further below.
Using the flow of exhaust gas from the fuel cell, which is generally still under superatmospheric pressure when it leaves the fuel cell, for regenerating the filter element, makes it possible to dispense with a pump dedicated to this purpose. In the case of conventional vehicles with an internal combustion engine, the regeneration of the filter element takes place by subatmospheric pressure in a suction pipe. In the case of vehicles with fuel cells, such a subatmospheric pressure is no longer available.
An active carbon filter may be advantageously used as the filter element. Depending on requirements and the application, however, other types of filter are also conceivable, with the result that the invention is not restricted to active carbon filters.
The filter element may be connected to the discharge line for the oxidizing agent or to the discharge line for the fuel or else to both discharge lines. However, it must be ensured that the flow of exhaust gas can entrain the hydrocarbons located in the filter element. In an advantageous embodiment, the filter element is therefore connected to the discharge line for the oxidizing agent, in particular whenever oxygen is used as the oxidizing agent, an adequate amount of which is always present.
Methanol, benzene, methane, natural gas, coal gas, biogas or the like may, for example but not exclusively, be used as the fuel for the fuel cells from which the hydrogen is produced in subsequent processes. Atmospheric oxygen may be used, for example, as a suitable oxidizing agent.
The filter element can be advantageously connected via a connecting line to an arrangement for preparing/generating fuel for the fuel cell from the fuel located in the fuel tank. In this way, once it has flowed through the filter element and bound the hydrocarbons, the flow of exhaust gas from the fuel cell can be further used in the production of the fuel—for example hydrogen.
The filter element is advantageously connected via a connecting line to a burner. In this burner, which may be designed for example as a catalytic burner, the flow of exhaust gas from the fuel cell, which after leaving the filter element also contains hydrocarbons, is burned. The waste heat thereby produced can be used in generating/preparing the fuel, for instance for vaporizing the fuel in a device for gas treatment.
Consequently, passing on the stream of exhaust gas containing hydrocarbons has the additional advantage that the harmful hydrocarbons are burned and that the waste heat produced is not lost but can be utilized. Furthermore, there is no direct connection between the filter element and the atmosphere, with the result that unwanted discharge of hydrocarbons into the atmosphere during operation of the vehicle is prevented.
In a further embodiment, a valve, in particular a shut-off valve, may be provided in the connecting line between the filter element and the burner. Such a shut-off valve is advantageous if a leakage diagnosis is carried out in the fuel tank. In this case, the shut-off valve must be closed. The operating principle of such a leakage diagnosis is discussed in more detail further below.
The fuel tank may be advantageously connected to the filter element via a line, with a valve, in particular a tank protection valve designed as a pressure-relief valve, being provided in the line. T
Eck Karl
Habrich Jürgen
Herdeg Wolfgang
Keutz Markus
Klos Holger
Cohen & Pontani, Lieberman & Pavane
Kalafut Stephen
Mannesman AG
Martin Angela J.
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