Vehicle having a driving internal-combustion engine and having a fuel cell system for the power supply to electric consuming devices of the vehicle and method for operating such a vehicle

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VEHICLE HAVING A DRIVING operating temperature. The fuel cell is started when it INTERNAL-COMBUSTION ENGINE AND reaches the operating temperature, and thereafter an electric HAVING A FUEL CELL SYSTEM FOR THE drive motor, (fed by the fuel cell System) generates torque POWER SUPPLY TO ELECTRIC for movement of the vehicle, either alone or together with CONSUMING DEVICES OF THE VEHICLE the internal-combustion engine. (German Patent Document AND METHOD FOR OPERATING SUCH A 19913 7943)

VEHICLE

Due to an increase in the number of electric consuming

BACKGROUND AND SUMMARY OF THE devices in truckS and passenger cars, difficulties arise when INVENTION generators are used for the power Supply. At approximately This application claims the priority of German patent 15%, the efficiency of dynamos is unfavorable. Moreover, document 19928 102.5, filed Jun. 19, 1999, the disclosure when the vehicle is Stopped, the battery can only be loaded of which is expressly incorporated by reference herein. briefly in order to avoid impairing its Starting capacity. By The invention relates to a vehicle having an internal usinggenerators, fuel cells, which have a significantly higher efficiency combustion engine, a starter battery or buffer battery and a 15 than operation of the and can be operated independently of the internal-combustion engine, the power fuel cell System to Supply electric consuming devices of the Supply while the vehicle is stopped can be improved, even vehicle, and to a method for operating Such a vehicle. for vehicles with Several consuming devices. In a known vehicle which is driven by an internal In the future, pollutant emissions of motor Vehicles must combustion engine, a fuel cell System Supplies energy to the electric consuming devices of the internal-combustion example, also still be drastically reduced. The reduction of, for engine, and can be activated independently of the operation nitrogen oxides in exhaust gases of conventional of the internal-combustion engine. The fuel cell System also internal-combustion formed by means of engines, Such as diesel engines, is per continuous exhaust gas catalysts which

Supplies the internal-combustion engine with electric have a poor cold-starting behavior.

energy. Abattery connected with the fuel cell System outputs nitrogen oxides produced during a As the result, 90% of the driving cycle are caused current when the internal-combustion engine is Started, and 25 covers brief peak loads (German Patent Document DE 197 by the poor cold-Starting behavior of the currently used 03 171 A1). In this vehicle, the fuel cell is supplied with exhaust gas catalysts.

hydrogen, either from a tank or indirectly by reforming One object of the invention is to provide a vehicle that is liquid or gaseous fuels, by way of a controlled throttle. driven by an internal-combustion engine, and has a high Reaction air is supplied to the fuel cell by way of a capacity and high-efficiency power Supply unit. compressor, with a throttle connected on the output Side. Another object of the invention is to provide Such a A motor Vehicle driven by an internal-combustion engine vehicle in which the pollutant emission is greatly reduced in is also known which, instead of a dynamo, has a fuel cell phase. a relatively simple manner, including in the cold Starting System that provides the electric energy for operating con

Suming devices independently of the rotational Speed of the 35 Finally, still another object of the invention is to provide internal-combustion engine. In this motor vehicle, the a method for operating Such a vehicle. internal-combustion engine is Supplied with liquid fuel. These and other objects and advantages are achieved by Hydrogen is separated from the liquid fuel for the operation the vehicle according to the invention, in which the fuel cell of the fuel cell system. Only a portion of the hydrogen is System has an electrically heatable, autothermal reforming Separated from the fuel. The remaining fuel constituents are 40 reactor, to which air and water can be fed by assemblies in further utilized in the internal-combustion engine; that is, the vehicle and hydrocarbons can be fed from the fuel tank, gaseous constituents are feed to the internal-combustion for partial oxidation and vapor reforming. A shift reactor is engine directly or by way of a mixture formation device and connected behind the reforming reactor for reducing the liquid constituents are returned into the fuel tank. An inter carbon monoxide fraction On its output Side, the shift reactor mediate H Storage device provided in the Supply line 45 is connected on the one hand to the anode-side input of a fuel Supplies the fuel cell at the time of the Starting of the vehicle. cell, via a valve which is penetrable after the operating A battery is provided for Starting the fuel cell System and/or temperature has been reached in the shift reactor, and is a separating device for Separating the hydrogen from the connected on the other hand to the driving internal liquid fuel. (German Patent Document DE 19523 109 A1) combustion engine, via a bypass of the fuel cell, which can Another fuel cell System which has been Suggested for use 50 be blocked when the operating temperature has been reached with an internal-combustion engine Supplied with liquid fuel in the shift reactor. When the reforming reactor is heated from a tank, generates electric energy during the operation electrically, hydrogen-containing gas, which will be avail of the internal-combustion engine, at least for the electric able within a very short time, is burned in the internal devices provided for the operation of the internal combustion engine with the hydrocarbons delivered from combustion engine, and is connected with a buffer battery. In 55 the fuel tank. Pollutant emissions are reduced significantly this System, exhaust gases or heating gases, which are by the metered addition of hydrogen during the initial generated as the result of the combustion of the liquid fuel, operating minutes of the internal-combustion engine, are guided through at least one heat eXchanger in the fuel because a cleaner combustion of the hydrocarbons takes cell System until an operating temperature Sufficient for place as the result of the hydrogen.

operation of the fuel cell System is reached. (German Patent 60 "Autothermal” means in this case that the heat required Document 19913 795.1) for the process is provided in the educt itself by the partial Finally, a vehicle has also been Suggested which is oxidation. Heat will be Supplied by electric heating only propelled by an internal-combustion engine drive and by a when the engine is started. The hydrogen-containing gas fuel cell drive, with liquid fuel being used to supply both flows through the shift reactor and, in the process, heats it to Such drives. The internal-combustion engine drive is used to 65 its operating temperature. When the operating temperature Start the vehicle, and to permit its immediate movement in the shift reactor has been reached, the hydrogen thereafter, as well as to heat the fuel cell System to an containing gas is guided from the shift reactor into the fuel

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cell by opening the valve connected in front of the fuel cell Virtually immediately after the internal-combustion engine and blocking the bypass. The hydrogen will then be oxidized is Started. Because of the resulting improved combustion in at the anode of the fuel cell and the oxygen will be reduced the engine, the pollutant emission is significantly reduced, at the cathode, So that the fuel cell Supplies electric power for even in the cold Starting phase. After the fuel cell has started the electric consuming devices of the motor vehicle. its operation, the anode exhaust gas, which Still contains A pollutant reduction in the exhaust gases is achieved by hydrogen is Supplied to the internal-combustion engine the utilization of the hydrogen generated for the fuel cell together with the fuel, to reduce pollutant emissions. By during a time period in which the fuel cell has not yet started reducing pollutant emissions, it is possible to design the its operation because of a warm-up phase. It is unnecessary internal-combustion engine for higher combustion to provide a hydrogen tank, which is hard to integrate in the temperatures, which increases the efficiency of the engine vehicle because of its Volume and weight, for reducing the while maintaining nitrogen oxide emissions (which are pollutants. greater at higher combustion temperatures) at acceptable Because of the intensive use of energy for which the values. Simultaneously, the fuel cell also Supplies the current battery would have to be designed, the generation of hydro for a larger number of consuming devices which may have gen by electrolysis is not practical. 15 a high power requirement.

In a preferred embodiment, the residual anode gas output Water for the reforming reactor is preferably obtained by of the fuel cell is connected with a pipe extending to the Separation from the cathode exhaust gas and/or from the driving internal-combustion engine, and the bypass also exhaust gases of the internal-combustion engine, So that it is leads into the Same pipe. In this embodiment, the portion of no longer necessary Lo carry a large water Supply in the the hydrogen not consumed in the fuel cell, and other vehicle. Moreover, it is expedient for the air for the reform burnable constituents in the anode exhaust gas, are burned in ing reactor and the fuel cell to be branched off from the air the engine. Also after the cold Starting phase, hydrogen is flow for the driving internal-combustion engine, eliminating Still Supplied to the fuel taken from the tank, whereby, also the need for Separate units for compressing the air required when the exhaust gas catalyst has reached its operating 25 by the reforming reactor and the fuel cell. In particular, the temperature, a greater pollutant reduction is achieved in the hydrogen-containing gas is generated in the reforming reac exhaust gases in comparison to vehicles which do not have tor by the partial oxidation and vapor reforming with an the System according to the invention. The cathode-side understoichiometric combustion at an air ratio of less than 1, output of the fuel cell is preferably connected with a water than the ratio of water to carbon in the fuel being set to be more tank by way of a separator; and the reforming reactor is also Zero in order to avoid a Soot formation. connected to the water tank. In this case, water required for In another advantageous embodiment, liquid fuel is used the reforming process is recovered from the cathode exhaust to Supply the reforming reactor and the internal-combustion gaS. engine. In the case of diesel oil, the ratio of water to carbon In particular, an air Supply input of the reforming reactor is set to a value more than 1.

is connected with the air Supply device of the internal 35 Other objects, advantages and novel features of the combustion engine. The air for the internal-combustion present invention will become apparent from the following engine can be generated, for example, by a compressor detailed description of the invention when considered in which is connected on the output Side with the internal conjunction with the accompanying drawings. combustion engine or the device for the mixture formation BRIEF DESCRIPTION OF THE DRAWINGS and the reforming reactor. 40

In another preferred embodiment, the air ratio of the The FIGURE of the drawing is a basic diagram of a reforming process is Set to be less than 1, and the ratio of vehicle having a driving internal-combustion engine and a water to carbon is greater than 0. The hydrogen is generated fuel cell System according to the invention. by means of an understoichiometric combustion. The air ratios are preferably in the range of from 0.2 to 0.6,0.3 being 45 DETAILED DESCRIPTION OF THE DRAWINGS optimal. The schematically illustrated vehicle 1 is driven by an The objects of the invention are also achieved by a internal-combustion engine 2. A fuel tank 3 Supplies liquid method for operating a vehicle having an internal fuel to the internal-combustion engine 2 via a fuel pipe 4. combustion engine, a starter battery or a buffer battery and (For simplicity, the fuel pump and the devices for the a fuel cell System for Supplying energy to electric consuming 50 mixture formation on the internal-combustion engine 2 are devices of the vehicle equipped. According to the invention, not shown.) A fuel cell system 5 which supplies power to the after the driving internal-combustion engine is started, a electric consuming devices of the vehicle 1 contains an hydrogen-containing gas is generated from the fed educts autothermal reforming reactor 6, in which vapor reforming air, water and a fuel of hydrocarbons in an autothermal and a Superimposed partial oxidation take place. The reform reforming reactor electrically which is heated to the oper 55 ing reactor 6 has an electric heating circuit 7, which can be ating temperature. The hydrogen containing gas is Supplied applied to a starter battery or buffer battery 8 by means of a to the internal-combustion engine together with the hydro Switch 9.

carbon fuel by way of a shift reactor. After the shift reactor A shift reactor 10 connected behind the reforming reactor is heated to its operating temperature for reducing the carbon 6 oxidizes CO generated in the reforming reactor 6. The monoxide fraction in the hydrogen-containing gas, the 60 output of the shift reactor 10 is connected with a valve 11 by hydrogen-containing gas is no longer fed directly to the way of a pipe 12, from which a bypass 13 branches off, in internal-combustion engine. Rather, it is fed to a fuel cell which a shut-off valve or slide is arranged. The valve 11 is whose anode exhaust gases, together with the hydrocarbon connected with the anode-side input of a PEM fuel cell 15. fuel, are Supplied to the internal-combustion engine. The anode-side output 16 of the fuel cell 15, is combined The reforming reactor is electrically heated to its operat 65 with the bypass 13 to form a pipe 17 which extends to the ing temperature in a few Seconds, this, the hydrogen internal-combustion engine 2. The cathode-side output of containing gas is available for admixture with the fuels the fuel cell 15 is connected with a separator 18 which

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Separates water from the cathode exhaust gas and Supplies it c) Hydrogen is generated by preheating by means of a to water storage device 19. The water storage device 19 is Starter battery (8) in an autothermal reforming process connected by way of a pipe 20 with the reforming reactor 6. as early as after a few Seconds. By way of another pipe 21, the fuel tank 3 is connected with d) The reforming reactor (6) is a multi-fuel-type reactor the reforming reactor 6. (gasoline/diesel).

A compressor 22, which is driven by an exhaust gas e) The evaporation of water and gasoline is integrated in turbocharger 23, Supplies the air required by the internal combustion engine 2, via a pipe 24. A pipe 25, which the reforming reactor (6). branches off from the pipe 24 between the compressor 22 f) The autothermal reforming process is carried out by and the internal-combustion engine 2, Supplies air to the means of the educts water, air and hydrocarbons at an reforming reactor 6 by way of a branch26 and to the cathode air ratio of less than 1 and a water excess of more than side of the fuel cell 15 by way of a branch 27. 1.

At the Starting of the internal-combustion engine 2, the g) The water for the process is recovered from the engine Switch 9 is closed. The reforming reactor 6 receives air via exhaust gas and/or the cathode exhaust gas of the fuel the pipe 25 and the branch-off 26, liquid hydrocarbon fuel 15 cell (15).

from the fuel tank 3 by means of a fuel pump (not shown) h) The air for the reforming reactor (6) and the fuel cell and water from the water storage tank 19 via a pump (not is branched off from the air supply for the internal shown). In the autothermal, essentially adiabatically combustion engine (2).

operating, reforming reactor 6, a gas with the constituents

H, CO, CO, CH and H2O as well as the inert gas N is i) The hydrocarbons are taken from the fuel tank (3). generated from the educts water, air and hydrocarbons, by j) After the electric warm-up phase of the reforming means of a partial oxidation and vapor reforming. reactor, the power Supply can be Switched off because Furthermore, SO and COS are to be expected in the case the operating temperature is maintained by the process. of Sulfurous fuels. As a result of the electric preheating, the A conflict exists between the goals of efficiency in an reforming reactor 6 starts to operate as early as after 1 to 2 internal-combustion engine (which generally requires a high Seconds. Because the reforming reactor 6 generates the 25 combustion temperature) and the reduction of nitrogen oxide required heat itself, the electric heater is then Switched off. emissions (which generally requires a low combustion Product gas from the reforming reactor 6 passes through the temperature). As a result of the invention, pollutant emis shift reactor 10 to the bypass 13, which is open, while the Sions can be reduced in the cold Starting phase as well as Valve 11 is closed. The hydrogen-containing gas therefore during normal operation with a heated engine, by means of arrives by way of the pipe 17 in the internal-combustion a gas generating System outside the engine, which is simul engine 2 and improves the thermal combustion of the fuel. taneously used to generate electric current for operating the AS a result, pollutant emissions of the internal-combustion vehicle. The engine can therefore be adapted to a higher engine are Significantly reduced during the cold Starting phase in which known exhaust gas catalysts do not yet efficiency at higher combustion temperatures while unac perform effectively. 35 ceptable emissions are avoided.

When flowing through the shift reactor 10, the gas from The foregoing disclosure has been Set forth merely to the reforming reactor 6 heats the shift reactor 10 to its illustrate the invention and is not intended to be limiting. operating temperature in approximately 1 to 2 minutes. After Since modifications of the disclosed embodiments incorpo the reaching of the operating temperature (monitored by rating the Spirit and Substance of the invention may occur to Sensors, not shown), the shift reactor 10 Starts to operate. 40 perSons skilled in the art, the invention should be construed The valve 11 is then opened up and the shut-off valve 14 is to include everything within the Scope of the appended closed, So that the hydrogen-containing gas flows out of the claims and equivalents thereof. What is claimed is:

shift reactor 10 into the fuel cell 15, to which simultaneously air is supplied by way of the branch-off 26. The fuel cell 1. A vehicle having an internal-combustion engine for Starts to operate and Supplies the electric consuming devices 45 propulsion, a fuel cell System for Supplying power to electric with current. The hydrogen-containing residual anode gas consuming devices of the vehicle, and a starter or buffer flows through the pipes 16, 17 to the internal-combustion battery, wherein the fuel cell System comprises: engine, and improves the combustion of the hydrocarbons, an electrically heatable, autothermal reforming reactor whereby pollutant emissions are also reduced after the cold which is coupled to receive air and water from Systems Starting phase. 50 on board the vehicle and hydrocarbons from the fuel

For generating hydrogen in the reforming reactor, an tank, for partial oxidation and vapor reforming, understoichiometric fuel combustion is Set, with air ratioS in a shift reactor connected to an output of the reforming the range of less than 1, particularly between 0.2 and 0.6, reactor for reducing a carbon monoxide fraction of gas with 0.3 being optimal. The S/C ratio, defined as the ratio of generated in the reforming reactor; and water to carbon, is to be above 0. Particularly in the case of 55 a fuel cell;

diesel oil as the fuel, S/C ratios of more than 1 are to be a valve connected between an output of the shift reactor desirable, in order to avoid Soot. and an anode input of the fuel cell, which Valve is The characteristics and the Significant advantage of the controllable to be open after an operating temperature invention are the following: has been reached in the shift reactor; and a) A fuel cell system (5) having a carbon reformer (6) 60 a bypass connected between the output of the shift reactor replaces the generator (increasing the efficiency) and and the internal-combustion engine, which bypass can contributes to the lowering of the pollutant emission of be blocked when the operating temperature has been the conventional internal-combustion engine (fuel cell/ reached in the shift reactor.

internal-combustion engine tandem arrangement). 2. The vehicle according to claim 1, wherein the residual b) The residual anode gas of the fuel cell is used to 65 anode gas output of the fuel cell is connected with a pipe improve the exhaust gas ratioS in the internal extending to the driving internal-combustion engine, the combustion engine. bypass also leading into this pipe.

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3. The vehicle according to claim 1, wherein the cathode hydrocarbon fuel until the shift reactor reaches an Side output of the fuel cell is connected by way of a separator operating temperature thereof; and with a water tank which is connected to Supply water to the after the Shift reactor reaches its operating temperature, reforming reactor. discontinuing Supplying the hydrogen-containing gas 4. The vehicle according to claim 1, wherein an air Supply to the driving internal-combustion engine, and Supply input of the reforming reactor is connected with an air

Supply device of the internal-combustion engine. ing Said hydrogen containing gas instead to the fuel cell 5. The vehicle according to claim 1, wherein the air ratio whose anode exhaust gases, together with the hydro of the reforming process is Set to less than 1 and the ratio of carbon fuel, are Supplied to the driving internal water to carbon is more than 0. combustion engine.

6. A method for operating a vehicle having an internal 7. The method according to claim 6, wherein water for the combustion engine for propulsion, a fuel cell System for reforming reactor is obtained by Separation from one of Supplying power to electric consuming devices of the cathode exhaust gas and internal-combustion engine exhaust vehicle, and a starter or buffer battery, the fuel cell system gaSeS.

including a fuel cell having an anode Side output connected 15 8. The method according to claim 6, wherein the air for to a fuel Supply input of the internal-combustion engine, an the reforming reactor and the fuel cell is branched off from electrically heatable autothermal reforming reactor for gen an air flow for the internal-combustion engine. erating a hydrogen containing gas, and a shift reactor 9. The method according to claim 6, wherein the connected to an output of the reforming reactor for reducing hydrogen-containing a carbon monoxide fraction of the hydrogen containing gas, gas is generated in the reforming reac an output of the shift reactor being Selectively connectable tor by the partial oxidation and vapor reforming with an to an anode gas input of the fuel cell and to a bypass line understoichiometric combustion, at an air ratio of less than which connects to Said fuel Supply input of the internal 1, the ratio of water to carbon in the hydrocarbons being Set combustion engine, Said method comprising: to a value greater than Zero by means of Supplied flows of upon Starting of the internal-combustion engine, heating 25 water and of hydrocarbon.

the reforming reactor to an operating temperature, 10. The method according to claim 9, wherein the air ratio thereof; is in the range of from 0.2 to 0.6.

Said reforming reactor generating hydrogen-containing 11. The method according to claim 9, wherein gas from fed educts air and water, and a fuel of diesel oil is the fuel; and hydrocarbons, the ratio of water to carbon is greater than 2. initially Supplying a gas output of the shift reactor via the bypass to the internal-combustion engine together with