Exhaust Treatment System With Hydrocarbon Lean NOx Catalyst

Abstract

A system for treating an exhaust stream from an engine includes a main exhaust passageway adapted to receive the exhaust stream from the engine. A side branch is in communication with the main exhaust passageway. A regeneration unit is positioned within the side branch for combusting a fuel and heating the exhaust flowing through the main exhaust passageway. A lean NO x catalyst is positioned within the main exhaust passageway downstream of the regeneration unit. A reductant injector is positioned downstream of the regeneration unit and upstream of the lean NO x catalyst to inject reductant particles into the exhaust stream. A controller operates the regeneration unit to increase the exhaust temperature as well as operates the reductant injector to reduce NO x within the lean NO x catalyst.

1 . A system for treating an exhaust stream from an engine, the system comprising:
 a main exhaust passageway adapted to receive the exhaust stream from the engine;   a side branch in communication with the main exhaust passageway;   a regeneration unit positioned within the side branch for combusting a fuel and heating the exhaust flowing through the main exhaust passageway;   a lean NO x  catalyst positioned within the main exhaust passageway downstream of the regeneration unit;   a reductant injector positioned downstream of the regeneration unit and upstream of the lean NO x  catalyst to inject reductant particles into the exhaust stream; and   a controller to operate the regeneration unit to increase the exhaust temperature as well as operate the reductant injector to reduce NO x  within the lean NO x  catalyst.   
     
     
         2 . The system of  claim 1 , further including an oxidation catalyst and a particulate filter positioned within the main exhaust passageway downstream of the regeneration unit and upstream of the reductant injector. 
     
     
         3 . The system of  claim 2 , further including a selective catalytic reduction device positioned downstream of the lean NO x  catalyst. 
     
     
         4 . The system of  claim 3 , wherein the oxidation catalyst and the particulate filter are positioned in a first housing, the lean NO x  catalyst and the selective catalytic reduction device being positioned in a second housing spaced apart from the first housing. 
     
     
         5 . The system of  claim 1 , wherein the lean NO x  catalyst includes a catalyst coated particulate filter. 
     
     
         6 . The system of  claim 5 , wherein the reductant injector is positioned downstream of the oxidation catalyst and further including a selective catalytic reduction device positioned downstream of the lean NO x  catalyst. 
     
     
         7 . The system of  claim 1 , wherein the reductant injector includes an aerosol generator for heating and injecting reductant. 
     
     
         8 . The system of  claim 7 , wherein the aerosol generator supplies reductant particles having a size less than one micron in diameter. 
     
     
         9 . The system of  claim 1 , further including an oxidation catalyst and a particulate filter positioned within the main exhaust passageway downstream of the lean NO x  catalyst. 
     
     
         10 . The system of  claim 1 , further including a hydrocarbon injector positioned downstream of the regeneration unit and upstream from an oxidation catalyst to inject a hydrocarbon into the exhaust stream. 
     
     
         11 . The system of  claim 1 , further including a particulate filter having a selective catalytic reduction material coating, the coated filter being positioned downstream of the lean NO x  catalyst. 
     
     
         12 . The system of  claim 1 , wherein the reductant injector injects an internal combustion engine fuel. 
     
     
         13 . The system of  claim 12 , wherein the regeneration unit is positioned immediately upstream of the lean NO x  catalyst to provide exhaust at a temperature high enough to burn carbon deposits from active sites within the lean NO x  catalyst. 
     
     
         14 . A system for treating an exhaust stream from an engine, the system comprising:
 an exhaust passageway adapted to receive the exhaust stream from the engine;   a burner for combusting a fuel and heating the exhaust flowing through the exhaust passageway;   a lean NO x  catalyst positioned within the exhaust passageway downstream of the burner;   a reductant injector positioned upstream of the burner and upstream of the lean NO x  catalyst to inject reductant particles into the exhaust stream; and   a controller to operate the burner to increase the exhaust temperature as well as operate the injector to reduce NO x  within the lean NO x  catalyst.   
     
     
         15 . The system of  claim 14 , further including a particulate filter having a selective catalytic reduction material coating, the coated filter being positioned downstream of the lean NO x  catalyst. 
     
     
         16 . The system of  claim 14 , wherein the reductant injector includes an aerosol generator for heating and injecting a hydrocarbon reductant. 
     
     
         17 . The system of  claim 16 , wherein the aerosol generator supplies reductant particles having a size less than one micron in diameter. 
     
     
         18 . The system of  claim 14 , wherein the reductant includes an alcohol based fuel. 
     
     
         19 . The system of  claim 14 , wherein the burner includes a shell around which an exhaust and reductant mixture flows, the burner generating a flame positioned within the shell. 
     
     
         20 . A system for treating an exhaust stream from an engine, the system comprising:
 an exhaust passageway adapted to receive the exhaust stream from the engine;   a burner for combusting a fuel and heating the exhaust flowing through the exhaust passageway;   a lean NO x  catalyst positioned within the exhaust passageway in direct receipt of the exhaust heated by the burner prior to passing through another catalyst;   a hydrocarbon injector positioned downstream of the burner and upstream of the lean NO x  catalyst to inject hydrocarbon into the exhaust stream; and   a controller to operate the burner to increase the exhaust temperature to a predetermined magnitude for burning carbon deposits positioned at active sites within the lean NO x  catalyst.   
     
     
         21 . The system of  claim 20 , wherein the hydrocarbon includes an alcohol based fuel. 
     
     
         22 . The system of  claim 20 , wherein the hydrocarbon includes diesel fuel. 
     
     
         23 . The system of  claim 20 , further including an oxidation catalyst and a particulate filter positioned within the main exhaust passageway downstream of the regeneration unit. 
     
     
         24 . The system of  claim 20 , wherein the reductant injector includes an aerosol generator for heating and injecting the hydrocarbon. 
     
     
         25 . The system of  claim 24 , wherein the aerosol generator supplies reductant particles having a size less than one micron in diameter.