Methods and apparatus for operating an emission abatement assembly

Abstract

A diesel exhaust system includes a supply of diesel fuel. The system further includes a first reduction path having a diesel fuel-fired burner operated to partially oxidize diesel fuel supplied thereto from the supply of diesel fuel and to introduce at least one of CO and H 2 into an exhaust stream. The first reduction path further includes an oxidation catalyst and a first emissions reduction component that is configured to be regenerated by CO and H 2 in the exhaust system. An associated method is disclosed.

1 . A diesel exhaust system comprising: 
 a supply of diesel fuel, and    a first reduction path having:    (i) a diesel fuel-fired burner operated to partially oxidize diesel fuel supplied thereto from the supply of diesel fuel and to introduce at least one of CO and H 2  into an exhaust stream,    (ii) an oxidation catalyst, and    (iii) a first emissions reduction component, the first emissions reduction component being configured to be regenerated by CO and H 2  in the exhaust stream.    
   
   
       2 . The system of  claim 1 , wherein: 
 the oxidation catalyst is positioned downstream of the diesel fuel-fired burner and configured to catalyze a reaction between oxygen present in the exhaust stream and the partially-oxidized diesel fuel to introduce at least one of CO and H 2  into the exhaust stream, and    the first emissions reduction component is positioned downstream of the oxidation catalyst.    
   
   
       3 . The system of  claim 1 , wherein the first emission reduction component includes a catalytic NOx absorber.  
   
   
       4 . The system of  claim 3 , wherein the burner is periodically operated at a fuel-to-air mixture providing increased production of at least one of CO or H 2 .  
   
   
       5 . The system of  claim 3 , further comprising a particulate filter disposed in the exhaust stream between the oxidation catalyst and the NOx absorber.  
   
   
       6 . The system of  claim 5 , wherein: 
 the burner is operable to heat the exhaust stream to a first temperature,    the oxidation catalyst is configured to further heat the exhaust stream to a second temperature greater than the first temperature, and    the second temperature is sufficient for at least one of incinerating a substantial portion of the particulates trapped by the filter or removing SO X  from the NOx absorber.    
   
   
       7 . The system of  claim 1 , further comprising a bypass path for periodically redirecting at least a substantial portion of the exhaust stream from the first reduction path.  
   
   
       8 . The system of  claim 7 , further comprising at least one valve capable of selectively directing a substantial portion of the exhaust stream from the first reduction path to the bypass path.  
   
   
       9 . The system of  claim 1 , further comprising a second reduction path, having: 
 a second diesel fuel-fired burner operated to burn at least a first portion of diesel fuel supplied thereto from the supply of diesel fuel and to introduce at least one of CO and H 2  into an exhaust stream,    a second oxidation catalyst, and    a second emissions reduction component positioned downstream of the second diesel fuel-fired burner, the second emissions reduction component being configured to be regenerated by CO and H 2  in the exhaust stream, and    at least one valve operable to selectively direct portions of the exhaust stream between the first and the second reduction paths.    
   
   
       10 . The system of  claim 9 , wherein: 
 the oxidation catalyst is disposed downstream of the diesel fuel-fired burner and upstream of the emissions reduction component and configured to catalyze a reaction between oxygen present in the exhaust stream and the partially-oxidized diesel fuel to introduce at least one of CO and H 2  into the exhaust stream, and    the second oxidation catalyst is disposed downstream of the second diesel fuel-fired burner and upstream of the second emissions reduction component and configured to catalyze a reaction between oxygen present in the exhaust stream and the partially-oxidized diesel fuel to introduce at least one of CO and H 2  into the exhaust stream.    
   
   
       11 . The system of  claim 9 , wherein the first and the second emissions reduction components include NOx absorbers.  
   
   
       12 . A method of operating a diesel exhaust system, the comprising the steps of: 
 advancing an exhaust stream along a reduction path having an oxidation catalyst,    operating a diesel fuel-fired burner to oxidize diesel fuel supplied thereto and to introduce at least one of CO or H 2  into the exhaust stream, and    directing the exhaust stream to a first NO X  absorber positioned along the reduction path to regenerate the NO X  absorber.    
   
   
       13 . The method of  claim 12 , wherein the operating step comprises processing an enriched fuel-to-air mixture of diesel fuel with the diesel fuel-fired burner.  
   
   
       14 . The method of  claim 12 , further comprising the step of filtering particulate matter from the exhaust stream with a particulate matter filter.  
   
   
       15 . The method of  claim 14 , further comprising the step of operating the burner to increase the temperature of the exhaust stream to a first temperature.  
   
   
       16 . The method of  claim 12 , further comprising: 
 the step of operating the burner to increase the temperature of the exhaust stream to a first temperature sufficient to remove SO X  from the NO X  absorber.    
   
   
       17 . The method of  claim 12 , wherein the directing step comprises directing a substantial portion of the exhaust stream to bypass the first NO X  absorber.  
   
   
       18 . The method of  claim 12 , further comprising the steps of wherein the directing step comprises redirecting a substantial portion of the exhaust stream from the first NO X  absorber to a second NO X  absorber.