Chemistry: electrical current producing apparatus – product – and – Having magnetic field feature
Reexamination Certificate
2000-11-30
2003-04-01
Maples, John S. (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Having magnetic field feature
C429S010000, C429S006000
Reexamination Certificate
active
06541143
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fuel cell system with a device for supplying fuel to the fuel cell.
2. Description of the Related Art
Fuel cells have long been known and have gained considerably in significance in recent years, especially in the area of the automobile industry.
In a fuel cell, current is produced by a chemical reaction. This involves converting a fuel and an oxidizing agent into electrical energy and water as reaction products. A fuel cell essentially comprises an anode part, a membrane and a cathode part. The membrane consists of a gas-impermeable and proton-conducting material and is arranged between the anode and the cathode in order to exchange ions. On the anode side, the fuel is fed in, while on the cathode side the oxidizing agent is fed in. At the anode, protons or hydrogen ions are generated by catalytic reactions and move through the membrane to the cathode. At the cathode, the hydrogen ions react with the oxygen and water is formed. The electrons given off during the reaction can be conducted as electric current through a load, for example the electric motor of an automobile.
Used for example as gaseous reactants for the fuel cell are hydrogen as the fuel and oxygen or air as the oxidizing agent.
If it is desired to operate the fuel cell with an energy source which is easily available or easily stored, such as natural gas, methanol or the like, these hydrocarbons must generally first be converted, initially into a hydrogen-rich gas, in a corresponding device for producing/preparing a fuel for a fuel cell, as is known for example from DE 198 23 499 A1. However, fuel cells which do not require such a prior conversion also already exist. For instance, EP 0 778 631 A1 discloses a fuel cell which is operated with a methanol/water mixture as the fuel.
The fuel or the starting material for the fuel is usually not introduced into the device for producing/preparing the fuel or the fuel cell in its pure form but as a motor-fuel/water mixture. For this reason, the motor fuel or the starting material for the fuel must initially be mixed with a suitable amount of water.
For the delivery of liquid media, so-called dual pumps, which respectively comprise two separate pumps within a common housing and are usually operated by means of a common drive, have been used for many years. For instance, DE 298 18 704 U1 discloses a dual pump which is used for example for the delivery of two different cooling flows in a cooling system. DE 197 10 675 A1 discloses a dual pump which is intended in particular for the delivery of heating water and comprises two pumps which are designed for delivery flows of distinctly different magnitudes and the rotational speeds of which are regulated individually or jointly, according to choice, by a pump control system and are operated over a great range of the total delivery rate. Furthermore, DE 195 36 997 C1 discloses a dual pump of an axial-piston type of design, which provides a joint suction line for both pumps, in which line a centrifugal pump is arranged for creating a suitable admission pressure for the two pumps of the dual pump. Furthermore, DE 30 41 832 A1 discloses an axial-piston dual pump for high-performance hydraulics. Finally, DE 35 44 016 C2 is concerned with a pump arrangement designed as a dual pump for the metered dispensing of at least 2 components with an adjustable mixing ratio. For this purpose, the two pumps of the dual pump are respectively provided with a swept-volume adjusting device, the two adjusting devices being connected to each other for joint symmetrical adjustment.
SUMMARY OF THE INVENTION
The present invention is based on the object of improving a fuel cell system of the generic type to the extent that a required motor-fuel/water mixture can be prepared and introduced into the device for producing/preparing the fuel or directly into the fuel cell in as simple and low-cost a way as possible.
This object is achieved according to the invention by a fuel cell system with a fuel cell which has an anode part with a supply line and a discharge line for a fuel and a cathode part with a supply line and a discharge line for an oxidizing agent, and with a device for supplying the fuel to the fuel cell either directly or via a device for producing/preparing the fuel, which is connected on the outlet side to the fuel supply line and on the inlet side to the device for supplying fuel, wherein the device for supplying fuel has a motor-fuel tank from which a motor-fuel supply line is led out. Also provided is a dual pump, which is likewise arranged in the motor-fuel supply line and is also connected to a water supply line. Finally, an intermediate tank is provided for the intermediate storage of the motor-fuel/water mixture and is likewise arranged in the motor-fuel line, downstream of the dual pump in the direction of flow.
The device according to the invention makes it possible in a simple and low-cost way to prepare a required motor-fuel/water mixture and to make it available to the device for producing/preparing the fuel or directly to the fuel cell.
In this case, the starting material for the fuel of the fuel cell is initially stored as motor fuel in the motor-fuel tank. If hydrogen is used as fuel for the fuel cell, the motor fuel may be, for example, methanol, methane, gasoline, natural gas, coal gas, biogas or the like.
The motor fuel is fed into the dual pump via the motor-fuel supply line. The dual pump is also connected to a corresponding water supply line. Such a dual pump has the effect that the motor fuel pumped out of the motor-fuel tank, serving as the starting material for the fuel, is mixed with the water, initially to form a motor-fuel/water mixture, before entering the device for producing/preparing the fuel or into the fuel cell.
This mixture produced in the dual pump is then intermediately stored in an intermediate tank, before it is fed into the device for producing/preparing the fuel or into the fuel cell.
The intermediate tank serves as a buffer store, so that a sufficient amount of motor-fuel/water mixture is always available for operating the device for producing/preparing the fuel or for operating the fuel cell. The presence of a sufficient amount of motor-fuel/water mixture is of significance in particular in the starting phase or running-up phase of the fuel cell system. During the starting phase of the fuel cell system—especially during cold starting—it is necessary to introduce the motor-fuel/water mixture as quickly as possible into the device for producing/preparing the fuel or into the fuel cell, in order that the fuel cell reaches its optimum performance capability as quickly as possible. The use of an intermediate tank in the motor-fuel supply line achieves the effect that a sufficient amount of motor-fuel/water mixture always remains in the fuel cell system—especially also after switching off the fuel cell—, so that when the fuel cell system is started again the motor-fuel/water mixture does not first have to be produced but is available right away.
Water which is discharged from the fuel cell during the fuel cell process and is recovered from the exhaust-gas flows from the fuel cell is advantageously used for the dual pump. This solution is explained in more detail in the further course of the description, without intending to restrict the invention to this one solution. The water supplied to the dual pump via the water supply line may, however, also be supplied from an external water source.
The device according to the invention for supplying fuel makes it possible in a simple way to prepare a motor fuel before it is further used as an intermediate product by mixing in process water right at the beginning of the process sequence in order to produce the corresponding motor-fuel/water mixture.
A further pump may advantageously be provided in the motor-fuel supply line upstream of the dual pump in the direction of flow of the motor fuel. By means of this pump, which is designed for example as a motor-fuel pump, the motor fuel o
Eck Karl
Habrich Jürgen
Herdeg Wolfgang
Hess Sabine
Klos Holger
Atecs Mannesmann AG
Cohen & Pontani, Lieberman & Pavane
Maples John S.
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