Exhaust treatment system and method of operation

Abstract

An exhaust treatment system is provided. Method of increasing activation of NOx reduction catalyst using two or more reductant is discussed. The exhaust treatment system includes an exhaust source, a reductant source, a nitrogen oxide (NOx) reduction catalyst, a sensor, and a controller. The reductant source includes a first reductant and second reductant, and is disposed to inject a reductant stream into an exhaust stream from the exhaust source. The NOx catalyst is disposed to receive both the exhaust stream and reductant stream. The sensor is disposed to sense a system parameter related to carbon loading of the catalyst and produce a signal corresponding to the system parameter. The controller is disposed to receive the signal and to control dosing of the reductant stream based at least in part on the signal.

1 . An exhaust treatment system comprising:
 an exhaust source;   a reductant source disposed to inject a reductant stream into an exhaust stream from the exhaust source, the reductant source comprising a first reductant and second reductant;   a nitrogen oxide (NOx) reduction catalyst disposed to receive the exhaust stream and the reductant stream;   a sensor disposed to sense a system parameter related to carbon loading of the catalyst, and produce a signal corresponding to the system parameter; and
 a controller disposed to receive the signal and to control dosing of the reductant stream based at least in part on the signal. 
   
     
     
         2 . The system of  claim 1 , wherein the controller is disposed to control the dosing by varying a ratio of the second reductant to the first reductant, a flow rate of first reductant, a flow rate of second reductant, or a combination of any of the foregoing. 
     
     
         3 . The system of  claim 2 , wherein the first reductant comprises diesel, biodiesel, ultra low sulphur diesel, Fischer-Tropsch fuel, kerosene, or any combinations thereof. 
     
     
         4 . The system of  claim 2 , wherein the second reductant comprises ethanol, methanol, isopropyl alcohol, n-propanol, n-butanol, methyl tert-butyl ether, E85, gasoline, or any combinations thereof. 
     
     
         5 . The system of  claim 2 , wherein the controller is configured to cause a ratio of the second reductant to the first reductant in the reductant stream to be greater than 0.5 when an estimated carbon loading exceeds a predetermined value. 
     
     
         6 . The system of  claim 5 , wherein the controller is configured to cause a ratio of the second reductant to the first reductant in the reductant stream to be greater than 3 when an estimated carbon loading exceeds a predetermined value. 
     
     
         7 . The system of  claim 6 , wherein the predetermined value is greater than about 1 weight percent of the catalyst. 
     
     
         8 . The system of  claim 1 , wherein the system parameter related to carbon loading comprises an exhaust stream composition parameter, an exhaust stream temperature parameter, an exhaust stream flow parameter, an exhaust source parameter, a time parameter, or a combination thereof. 
     
     
         9 . The system of  claim 8 , wherein the exhaust stream composition parameter comprises a concentration of NOx in the exhaust stream and a space velocity of the catalyst. 
     
     
         10 . The system of  claim 9 , wherein the predetermined NOx concentration value is in the range of 1 to 2000 ppmV. 
     
     
         11 . The system of  claim 9 , wherein the catalyst space velocity is between 1000 hr −1  and 200,000 hr −1 . 
     
     
         12 . The system of  claim 8 , wherein the exhaust stream temperature parameter comprises temperature of the catalyst and temperature of the exhaust stream. 
     
     
         13 . The system of  claim 12 , wherein the exhaust temperature is between about 200° C. and about 650° C. 
     
     
         14 . The system of  claim 8 , wherein the exhaust stream flow parameter comprises a molar, mass, and volumetric flow rate of the exhaust stream, reductant stream, and air stream. 
     
     
         15 . The system of  claim 14 , wherein a ratio of the molar flow rate of carbon in the reductant stream to the molar flow rate of nitrogen in NOx in the exhaust stream is between 0 and 12. 
     
     
         16 . The system of  claim 8 , wherein the exhaust source parameters comprises source speed, torque, and source power. 
     
     
         17 . The system of  claim 1 , wherein the first reductant is a fuel and the second reductant is an oxygenate. 
     
     
         18 . The system of  claim 17 , wherein the second reductant comprises ethanol. 
     
     
         19 . The system of  claim 1 , wherein the catalyst comprises a hydrocarbon selective catalytic reduction (HC-SCR) catalyst. 
     
     
         20 . The system of  claim 19 , wherein the catalyst comprises silver and a templated metal oxide substrate. 
     
     
         21 . An exhaust treatment system, comprising:
 an exhaust source;   a reductant source comprising a first storage place and a second storage place, wherein the first storage place is disposed to inject a fuel to the exhaust source and further configured to inject fuel to an exhaust stream emitted from the exhaust source, and the second storage place disposed to inject an oxygenate into the exhaust stream;   a nitrogen oxide reduction catalyst disposed to receive the exhaust stream, fuel, and the oxygenate;   a sensor disposed to sense a system parameter related to carbon loading of the catalyst, and produce a signal; and   a controller disposed to receive the signal, compare the signal with predetermined points, estimate the carbon loading, and increase a ratio of oxygenate to fuel in the exhaust stream, for a calculated duration of time, wherein the system parameter is a post-catalyst NOx concentration, a space velocity of the catalyst, temperature of the catalyst, temperature of the exhaust stream, a flow rate of the exhaust stream, or combinations thereof.   
     
     
         22 . The system of  claim 21 , wherein the first storage place comprises a fuel comprising diesel, biodiesel, ultra low sulphur diesel, Fischer-Tropsch fuel, kerosene or any combinations thereof. 
     
     
         23 . The system of  claim 21 , wherein the second storage place comprises an oxygenate comprising ethanol, methanol, isopropyl alcohol, n-propanol, n-butanol, methyl tert-butyl ether, gasoline, E85, or any combinations thereof. 
     
     
         24 . The system of  claim 21 , wherein the ratio of oxygenate to fuel is greater than 3. 
     
     
         25 . An exhaust treatment system comprising:
 an exhaust source;   a reductant source disposed to inject a reductant stream into an exhaust stream from the exhaust source, the reductant source comprising a first reductant and second reductant;   a nitrogen oxide (NOx) reduction catalyst disposed to receive the exhaust stream and the reductant stream;   a sensor disposed to sense a system parameter related to carbon loading of the catalyst, and produce a signal corresponding to the system parameter; and   a controller disposed to receive the signal and to control temperature of the exhaust stream and dosing of the reductant stream based at least in part on the signal.