Method and apparatus for desulfurizing a NOx trap

Abstract

An emission abatement system comprises a plurality of NO X traps positioned in a parallel flow arrangement, a desulfurization agent supplier for supplying a desulfurization agent, a valve arrangement for directing flow of the desulfurization agent and internal combustion engine exhaust gas between the NO X traps, and a controller. The controller is used to control operation of the desulfurization agent supplier and the valve arrangement to desulfurize the NO X traps. An associated method is disclosed.

1 . A method of desulfating a NO X  trap including the steps of: 
 operating a fuel reformer so as to produce a reformate gas comprising hydrogen and carbon monoxide,    advancing the reformate gas into the NO X  trap to react the hydrogen and carbon monoxide with SO X  trapped on the NO X  trap to remove SO X  from the NO X  trap, and    raising the temperature within the NO X  trap during the advancing step.    
     
     
         2 . The method of  claim 1 , wherein the step of raising the temperature within the NO X  trap includes raising the temperature of exhaust gases advancing through the NO X  trap from an internal combustion engine.  
     
     
         3 . The method of  claim 2 , wherein the step of raising the temperature further includes reducing an air-to-fuel ratio of an air/fuel mixture being introduced into the internal combustion engine.  
     
     
         4 . The method of  claim 1 , wherein raising the temperature further includes raising the NO X  trap to a temperature less than about 650° C.  
     
     
         5 . The method of  claim 1 , further including the step of determining if the NO X  trap is to be purged of SO X  and generating a purge-SO X  signal in response thereto, and wherein the advancing step further includes advancing the reformate gas into the NO X  trap to remove SO X  from the NO X  trap in response to generation of the purge-SO X  signal.  
     
     
         6 . The method of  claim 5 , wherein the determining step comprises determining if a predetermined period of time has elapsed since the NO X  trap was last purged of SO X  and generating a time-lapsed control signal in response thereto, and the advancing step further includes advancing the reformate gas into the NO X  trap to remove SO X  from the NO X  trap in response to generation of the time-lapsed control signal.  
     
     
         7 . The method of  claim 5 , wherein the determining step comprises sensing the amount of SO X  within the NO X  trap.  
     
     
         8 . The method of  claim 7 , wherein: 
 the sensing step includes the step of generating a trap-saturated control signal when the amount of SO X  within the NO X  trap reaches a predetermined accumulation level, and    the advancing step includes advancing the reformate gas into the NO X  trap to remove the SO X  within the NO X  trap in response to the generation of the trap-saturated control signal.    
     
     
         9 . A method of desulfurizing a plurality of NO X  traps positioned in a parallel flow arrangement, the method comprising the steps of: 
 determining if desulfurization of the NO X  traps is to be performed and generating a desulfurization signal in response thereto, and    advancing, in response to the desulfurization signal, (i) a desulfurization agent to the NO X  traps in sequential order for a plurality of cycles and (ii) internal combustion engine exhaust gas to each NO X  trap not receiving the desulfurization agent during the plurality of cycles.    
     
     
         10 . The method of  claim 9 , wherein the advancing step comprises blocking flow of the exhaust gas to whichever NO X  trap is receiving the desulfurization agent.  
     
     
         11 . The method of  claim 9 , wherein the advancing step comprises advancing the desulfurization agent to each NO X  trap for a predetermined period of time during each cycle.  
     
     
         12 . The method of  claim 9 , wherein the advancing step comprises operating a valve arrangement so as to control flow of the desulfurization agent and flow of the exhaust gas between the NO X  traps for the plurality of cycles.  
     
     
         13 . The method of  claim 9 , wherein: 
 each NO X  trap comprises a catalyst component for catalyzing oxidation and reduction reactions and a storage component for storing NO X , and    the advancing step comprises desulfurizing the catalyst component and the storage component of each NO X  trap.    
     
     
         14 . The method of  claim 9 , wherein the advancing step comprises (i) operating a plasma fuel reformer so as to produce a reformate gas comprising hydrogen and carbon monoxide and (ii) advancing the reformate gas to the NO X  traps in sequential order for the plurality of cycles.  
     
     
         15 . The method of  claim 9 , wherein the advancing step comprises advancing diesel fuel to the NO X  traps in sequential order for the plurality of cycles.  
     
     
         16 . A method of desulfurizing a plurality of NO X  traps positioned in a parallel flow arrangement, the method comprising the steps of: 
 determining if desulfurization of the NO X  traps is to be performed and generating a desulfurization signal in response thereto, and    advancing a desulfurization agent to the NO X  traps in sequential order for a plurality of cycles in response to the desulfurization signal.    
     
     
         17 . The method of  claim 16 , wherein the plurality of NO X  traps comprise first and second NO X  traps, and the advancing step comprises alternating a flow of the desulfurization agent and a flow of exhaust gas between the first and second NO X  traps for the plurality of cycles in response to the desulfurization signal.  
     
     
         18 . The method of  claim 17 , wherein the advancing step comprises moving a valve in response to the desulfurization signal a plurality of times between (i) a first position directing the flow of the desulfurization agent to the first NO X  trap and the flow of the exhaust gas to the second NO X  trap, and (ii) a second position directing the flow of the desulfurization agent to the second NO X  trap and the flow of the exhaust gas to the first NO X  trap.  
     
     
         19 . The method of  claim 16 , wherein the advancing step comprises cooling each NO X  trap not receiving the desulfurization agent with exhaust gas from an internal combustion engine during the plurality of cycles.  
     
     
         20 . The method of  claim 19 , wherein the advancing step comprises blocking flow of the exhaust gas to whichever NO X  trap is receiving the desulfurization agent.  
     
     
         21 . The method of  claim 16 , wherein the advancing step comprises (i) operating a fuel reformer so as to produce a reformate gas comprising hydrogen and carbon monoxide and (ii) advancing the reformate gas to the NO X  traps in sequential order for the plurality of cycles in response to the desulfurization signal.  
     
     
         22 . The method of  claim 16 , wherein the advancing step comprises advancing diesel fuel to the NO X  traps in sequential order for the plurality of cycles in response to the desulfurization signal.  
     
     
         23 . The method of  claim 16 , wherein the advancing step comprises advancing a desulfurization agent comprising diesel fuel and having a lambda value between about 0.4 and about 0.7 to the NO X  traps in sequential order for the plurality of cycles.  
     
     
         24 . An emission abatement system, comprising: 
 a plurality of NO X  traps positioned in a parallel flow arrangement,    a desulfurization agent supplier for supplying a desulfurization agent,    a valve arrangement for directing flow of the desulfurization agent and internal combustion engine exhaust gas between the NO X  traps, and    a controller electrically coupled to the desulfurization agent supplier and the valve arrangement, the controller comprising a processor and a memory device electrically coupled to the processor, the memory device having stored therein a plurality of instructions which, when executed by the processor, causes the processor to:    determine if desulfurization of the NO X  traps is to be performed and generate a desulfurization signal in response thereto, and    operate, in response to the desulfurization signal, the desulfurization agent supplier and the valve arrangement to advance (i) the desulfurization agent to the NO X  traps in sequential order for a plurality of cycles and (ii) the exhaust gas to each NO X  trap not receiving the desulfurization agent during the plurality of cycles.    
     
     
         25 . The emission abatement system of  claim 24 , wherein: 
 the plurality of NO X  traps comprise two NO X  traps, and    the plurality of instructions, when executed by the processor, further cause the processor to operate the valve arrangement to alternate a flow of the desulfurization agent and a flow of the exhaust gas between the two NO X  traps for the plurality of cycles in response to the desulfurization signal.    
     
     
         26 . The emission abatement system of  claim 24 , wherein the plurality of instructions, when executed by the processor, further cause the processor to operate the valve arrangement so as to block flow of exhaust gas to whichever NO X  trap is receiving the desulfurization agent.  
     
     
         27 . The emission abatement system of  claim 24 , wherein the plurality of instructions, when executed by the processor, further cause the processor to operate the desulfurization agent supplier and the valve arrangement to advance the desulfurization agent to each NO X  trap for a predetermined period of time during each cycle.  
     
     
         28 . The emission abatement system of  claim 24 , wherein: 
 the desulfurization agent supplier is a plasma fuel reformer, and    the plurality of instructions, when executed by the processor, further cause the processor to operate the plasma fuel reformer and the valve arrangement so as to advance a reformate gas produced by the plasma fuel reformer to the NO X  traps in sequential order for the plurality of cycles.    
     
     
         29 . The emission abatement system of  claim 24 , wherein: 
 the desulfurization agent supplier is a hydrocarbon supplier, and    the plurality of instructions, when executed by the processor, further cause the processor to operate the hydrocarbon supplier and the valve arrangement so as to advance hydrocarbons from the hydrocarbon supplier to the NO X  traps in sequential order for the plurality of cycles.