Exhaust treatment system

Abstract

An exhaust gas treatment system of an internal combustion engine includes a selective catalytic reduction catalyst fluidly connected to the internal combustion engine, an oxidation catalyst fluidly connected upstream of the selective catalytic reduction catalyst, and a particulate filter fluidly connected upstream of the selective catalytic reduction catalyst. The exhaust gas treatment system further includes a recirculation line configured to direct a portion of an exhaust flow of the internal combustion engine toward an inlet of the engine.

1 . An exhaust gas treatment system of an internal combustion engine, comprising:
 a selective catalytic reduction catalyst fluidly connected to the internal combustion engine;   an oxidation catalyst fluidly connected upstream of the selective catalytic reduction catalyst;   a particulate filter fluidly connected upstream of the selective catalytic reduction catalyst; and   a recirculation line configured to direct a portion of an exhaust flow of the internal combustion engine toward an inlet of the engine.   
   
   
       2 . The system of  claim 1 , further including at least one component configured to inject a flow of reductant upstream of the selective catalytic reduction catalyst. 
   
   
       3 . The system of  claim 1 , wherein the recirculation line is fluidly connected one of downstream of the oxidation catalyst, downstream of the particulate filter, or downstream of the selective catalytic reduction catalyst. 
   
   
       4 . The system of  claim 1 , wherein the recirculation line is fluidly connected downstream of an energy extraction assembly of the exhaust gas treatment system. 
   
   
       5 . The system of  claim 1 , wherein the oxidation catalyst is disposed on a substrate of the particulate filter. 
   
   
       6 . The system of  claim 1 , wherein the oxidation catalyst is configured to maintain a desired ratio of NO to NO 2  in an exhaust flow of the internal combustion engine. 
   
   
       7 . The system of  claim 1 , further including an NOx trap fluidly connected upstream of the oxidation catalyst. 
   
   
       8 . The system of  claim 7 , wherein the NOx trap is disposed between an outlet of the internal combustion engine and an energy extraction assembly of the exhaust gas treatment system. 
   
   
       9 . The system of  claim 1 , further including a catalyst fluidly connected downstream of the SCR catalyst. 
   
   
       10 . The system of  claim 1 , further including a ventilation line fluidly connected to a crankcase of the internal combustion engine. 
   
   
       11 . The system of  claim 1 , further including an energy extraction assembly configured to reduce the pressure of an exhaust flow of the internal combustion engine. 
   
   
       12 . An exhaust gas treatment system of an internal combustion engine, comprising:
 a selective catalytic reduction catalyst fluidly connected to the internal combustion engine;   an oxidation catalyst fluidly connected upstream of the selective catalytic reduction catalyst;   a particulate filter fluidly connected upstream of the selective catalytic reduction catalyst; and   a low pressure exhaust gas recirculation loop.   
   
   
       13 . The system of  claim 12 , wherein a component of the low pressure exhaust gas recirculation loop is fluidly connected one of downstream of the oxidation catalyst, downstream of the particulate filter, or downstream of the selective catalytic reduction catalyst, and the component is configured to direct a portion of an exhaust flow of the internal combustion engine toward an inlet of the internal combustion engine. 
   
   
       14 . The system of  claim 12 , wherein the oxidation catalyst is disposed on a substrate of the particulate filter. 
   
   
       15 . The system of  claim 12 , wherein the oxidation catalyst is configured to maintain a desired ratio of NO to NO 2  in an exhaust flow of the internal combustion engine. 
   
   
       16 . The system of  claim 12 , further including an NOx trap fluidly connected upstream of the oxidation catalyst. 
   
   
       17 . The system of  claim 12 , further including a catalyst fluidly connected downstream of the selective catalytic reduction catalyst. 
   
   
       18 . A method of an exhaust flow of an internal combustion engine, comprising:
 filtering the exhaust flow with a particulate filter;   oxidizing the exhaust flow with an oxidation catalyst;   catalytically reducing NOx contained in the filtered oxidized flow with a selective catalytic reduction catalyst; and   directing a portion of the exhaust flow to an inlet of the internal combustion engine.   
   
   
       19 . The method of  claim 18 , further including collecting NOx contained within the exhaust flow with an NOx trap fluidly connected upstream of the selective catalytic reduction catalyst. 
   
   
       20 . The method of  claim 18 , further including removing reductant from the exhaust flow with a catalyst fluidly connected downstream of the selective catalytic reduction catalyst.