Method and arrangement for reforming fuel

Abstract

A method and an arrangement for reforming a hydrocarbon fuel such as dimethyl ether (DME), methanol, ethanol, propanol, or any variants or other oxidized fuels is disclosed for generating hydrogen especially for supplying a fuel cell. Furthermore, a fuel cell system is disclosed which includes such an arrangement, especially for providing power to a stationary or mobile power consuming unit like especially an auxiliary power unit (APU) for application in aircraft, ships and vehicles, or as a part of a hybrid drive or as a sole driving unit for, e.g., a ship or a vehicle.

1 . Method for reforming a hydrocarbon fuel for generating hydrogen especially for operating a fuel cell, comprising a start-up phase with:
 a first stage in which the hydrocarbon fuel is reformed in a fuel reformer by an exothermic catalytic partial oxidation process (CPO or catalytic POx) to hydrogen;   a second stage in which the generated hydrogen is converted into water steam which is fed back into the fuel reformer; and   a third stage in which an endothermic catalytic steam reforming process is initiated in the fuel reformer by the water steam, so that by the combination of exothermic and the endothermic processes an autothermal fuel reforming process (ATR) is created; and   
       a steady state operation phase in which the hydrogen which is generated by the ATR process is fed to the fuel cell for operating the same. 
     
     
         2 . Method according to  claim 1 ,
 wherein an initial step is preceeding the first stage, in which hydrocarbon fuel and air is fed into the fuel reformer as a lean mixture such that the fuel reformer is catalytically started and heated by an exothermic reaction.   
     
     
         3 . Method according to  claim 1 ,
 wherein a fourth stage is following the third stage in which the hydrogen which is generated by the ATR process is purified prior to supplying it to the fuel cell, by especially reducing the amount of carbon monoxide.   
     
     
         4 . Method according to  claim 1 ,
 wherein a transition phase is preceeding the steady state operation in which a portion of the hydrogen which is generated by the ATR process is supplied to the fuel cell and another portion is converted into water steam, which is fed back into the fuel reformer.   
     
     
         5 . Method according to  claim 1 ,
 wherein a catalytic combustion reactor is used for conducting the second stage and wherein in the steady state operation, excess hydrogen which is generated by the fuel cell is supplied to the combustion reactor for catalytically converting the same into water steam, which is fed as a heat source to a heat exchanger in which water which is generated by the fuel cell is evaporated to steam which is fed into the fuel reformer.   
     
     
         6 . Method according to  claim 1 ,
 in which in the first stage oxygen is fed into the fuel reformer in the form of ambient air such that the lambda value of the air to fuel mixture is about 0.1 to 0.7.   
     
     
         7 . Method according to  claim 2 ,
 in which in the initial step oxygen is fed into the fuel reformer in the form of ambient air such that the lambda value of the air to fuel mixture is between about 4 and about 8.   
     
     
         8 . Arrangement for reforming a hydrocarbon fuel, especially according to a method of at least one of  claims 1  to  7 , for generating hydrogen especially for operating a fuel cell, wherein the arrangement comprises:
 a fuel reformer ( 1 ) containing an oxidation catalyst ( 1   a ), for generating hydrogen from supplied fuel and oxygen; and 
 a catalytic combustion reactor ( 3 ), for catalytically converting hydrogen into water steam; 
 
       wherein the fuel reformer ( 1 ) and the combustion reactor ( 3 ) are connected in a loop such that by the water steam from the combustion reactor ( 3 ) an autothermal fuel reforming process (ATR) can be created in the fuel reformer ( 1 ). 
     
     
         9 . Arrangement according to  claim 8 ,
 comprising a gas clean-up reactor ( 2 ) between an outlet of the fuel reformer ( 1 ) and an inlet of the combustion reactor ( 3 ) for reducing the amount of carbon monoxide from the product of the fuel reformer ( 1 ).   
     
     
         10 . Arrangement according to  claim 8 ,
 comprising a control unit ( 1   d ) for controlling the ratio of air to fuel supplied into the fuel reformer ( 1 ).   
     
     
         11 . Arrangement according to  claim 8 ,
 comprising a control unit ( 1   d ) for controlling inlet valves of the fuel reformer ( 1 ) so that the first stage according to  claim 1  and/or the initial step according to  claim 2  is realized.   
     
     
         12 . Arrangement according to  claim 8 ,
 comprising a fuel reformer ( 1 ) which comprises a catalyst ( 1   a ) with a multipurpose catalyst material or at least two one-purpose catalyst materials, for conducting endothermic steam reforming and exothermic oxidation processes.   
     
     
         13 . Control unit ( 1   d ) for controlling an arrangement according to at least one of  claims 8  to  11 . 
     
     
         14 . Fuel cell system for generating power by means of at least one fuel cell ( 4 ), comprising an arrangement according to at least one of  claims 8  to  11 . 
     
     
         15 . Fuel cell system according to  claim 14 ,
 in which hydrogen generated by the fuel cell ( 4 ) is supplied via a separator ( 7 ) to the combustion reactor ( 3 ) for generating heat for evaporating water of the fuel cell.   
     
     
         16 . Fuel cell system according to  claim 14 ,
 in which water generated by the fuel cell ( 4 ) is supplied via a separator ( 7 ) into a vessel ( 8 ) for generating steam for feeding the fuel reformer ( 1 ).   
     
     
         17 . Computer program comprising computer program code means adapted to perform a method according to at least one of  claims 1  to  7  when said program is run on a programmable microcomputer. 
     
     
         18 . Computer program according to  claim 17  adapted to be downloaded to an arrangement according to  claim 8  or a fuel cell system according to  claim 14  or one of its components when run on a computer which is connected to the interne. 
     
     
         19 . Computer program product stored on a computer readable medium, comprising computer program code means according to  claim 17 .