Emission control system and method

Abstract

A system includes an exhaust conduit configured to conduct a stream of exhaust gas, wherein the exhaust conduit comprises a selective catalytic reduction catalyst reactor comprising a first catalyst composition; an fuel source configured to introduce a fuel into the exhaust gas stream within the exhaust conduit upstream of the selective catalytic reduction catalyst reactor; a catalytic partial oxidation reformer in fluid communication with the exhaust gas stream and upstream from the selective catalytic reduction catalyst reactor, wherein the catalytic partial oxidation reformer can introduce a hydrogen-rich syngas co-reductant into the exhaust gas stream, when a temperature of the exhaust fluid is less than a determined threshold temperature.

1 . A system, comprising:
 an exhaust conduit configured to conduct a stream of exhaust gas, wherein the exhaust conduit comprises a selective catalytic reduction catalyst reactor comprising a first catalyst composition;   an fuel source configured to introduce a fuel into the exhaust gas stream within the exhaust conduit upstream of the selective catalytic reduction catalyst reactor;   a catalytic partial oxidation reformer in fluid communication with the exhaust gas stream and upstream from the selective catalytic reduction catalyst reactor, wherein the catalytic partial oxidation reformer can introduce a hydrogen-rich syngas co-reductant into the exhaust gas stream, when a temperature of the exhaust fluid is less than a determined threshold temperature.   
   
   
       2 . The system of  claim 1 , wherein the fuel comprises a selected one of a primary fuel and a secondary fuel. 
   
   
       3 . The system of  claim 1 , wherein the catalytic partial oxidation reformer comprises a second catalyst composition that can produce the hydrogen-rich syngas co-reductant from a primary fuel. 
   
   
       4 . The system of  claim 1 , wherein the fuel source is a secondary fuel source and the fuel is a secondary fuel. 
   
   
       5 . The system of  claim 1 , wherein the fuel source is a primary fuel source and the fuel is the primary fuel. 
   
   
       6 . The system of  claim 1 , further comprising a controller operable to control the flow of the primary fuel to the second catalyst and control the production of hydrogen-rich syngas co-reductant. 
   
   
       7 . The system of  claim 1 , wherein the determined temperature set point is about 375 degrees Celsius. 
   
   
       8 . The system of  claim 2 , wherein the secondary fuel comprises one or both of gasoline and a short chain alcohol. 
   
   
       9 . The system of  claim 1 , wherein the first catalyst composition comprises a catalyst material selected from the group consisting of gallium, indium, tungsten, molybdenum, bismuth, vanadium, and cobalt. 
   
   
       10 . The system of  claim 1 , wherein the first catalyst composition comprises a catalyst material selected from the group consisting of gallium oxide, indium oxide, molybdenum oxide, bismuth oxide, and cobalt oxide. 
   
   
       11 . The system of  claim 1 , wherein the first catalyst composition comprises one or both of tungsten oxide or vanadium oxide. 
   
   
       12 . The system of  claim 1 , wherein the first catalyst composition comprises silver. 
   
   
       13 . The system of  claim 1 , wherein the first catalyst composition consists essentially of silver, silver oxide, or both silver and silver oxide. 
   
   
       14 . The system of  claim 1 , wherein the first catalyst composition is a zeolyte. 
   
   
       15 . The system of  claim 14 , wherein the first catalyst composition comprises a selected one or all of a combination of silver with the zeolyte, tungsten oxide, and vanadium oxide. 
   
   
       16 . The system of  claim 3 , wherein the second catalyst composition is capable of performing a catalytic partial oxidation function of the primary fuel. 
   
   
       17 . The system of  claim 1 , wherein the second catalyst composition comprises a platinum group metal. 
   
   
       18 . The system of  claim 17 , wherein the platinum group metal comprises a metal selected from the group consisting of palladium, iridium, osmium, and ruthenium. 
   
   
       19 . The system of  claim 17 , wherein the platinum group metal comprises platinum or rhodium. 
   
   
       20 . The system of  claim 18 , wherein the second catalyst composition further comprises one or more promoter metals selected from Group VIII, Group IB, Group VB, or Group VIB of the Periodic Table of Elements. 
   
   
       21 . A method, comprising:
 determining a condition of an exhaust gas stream to be less than a determined threshold value;   responding to the exhaust gas stream condition being at or above the threshold value by flowing a co-reductant into the exhaust gas stream prior to the exhaust gas stream contacting a selective catalytic reduction catalyst; and   contacting the co-reductant, the exhaust gas stream and a fuel with the selective catalytic reduction catalyst to control a concentration of one or more components of the exhaust gas stream.   
   
   
       22 . The method of  claim 16 , wherein the condition is a selected one or both of an exhaust temperature and a concentration of an exhaust emission species. 
   
   
       23 . The method of  claim 16 , wherein determining the value includes sensing the condition directly or sensing an engine operating parameter. 
   
   
       24 . The method of  claim 23 , further comprising forming the co-reductant. 
   
   
       25 . The method of  claim 24 , wherein flowing the co-reductant comprises forming a hydrogen-rich syngas via partial oxidation of a primary fuel for an engine that is producing the exhaust gas stream. 
   
   
       26 . The method of  claim 24 , wherein forming the co-reductant is controlled to occur only on demand. 
   
   
       27 . The method of  claim 24 , wherein forming the co-reductant further comprises storing the co-reductant until needed. 
   
   
       28 . The method of  claim 24 , wherein the co-reductant is flowed continuously into the exhaust gas stream when the exhaust gas condition is at, or less than, the threshold value. 
   
   
       29 . The method of  claim 23 , further comprising controlling a flow rate or concentration of the co-reductant into the exhaust gas stream.