Thermal management of integrated emission reduction system

Abstract

The present invention involves thermal management of an integrated emission reduction system for the removal of particulate matter and NOx from diesel engine exhaust streams. The inventive integrated emission reduction system may include a diesel particulate filter (DPF), a heat source for adjusting the temperature of the exhaust stream entering the DPF, at least one catalytic absorber of NOx, a heat exchanger for adjusting the temperature of the exhaust stream entering the NOx absorber, and a computing device to monitor the temperature of the exhaust stream entering the DPF and the NOx absorber, and to control the operation of the heat exchanger and heat source, thereby improving the efficiency of the DPF and the NOx absorber.

What is claimed is:  
     
         1 . An exhaust emission reduction system for reducing exhaust stream emissions produced by a diesel engine, comprising: 
 a particulate filter contained within the exhaust stream;    a heat exchanger to adjust the temperature of the diesel exhaust stream; and    at least one catalytic absorber of NOx within the temperature adjusted diesel exhaust stream.    
     
     
         2 . The emission reduction system of  claim 1 , wherein the diesel engine is adapted for powering a vehicle.  
     
     
         3 . The emission reduction system of  claim 1 , further comprising a diesel oxidation catalyst within the exhaust stream.  
     
     
         4 . The emission reduction system of  claim 1 , wherein said at least one NOx absorber includes at least two NOx absorbers coupled in parallel; and the emission reduction system further comprises at least one valve capable of selectively directing the exhaust stream to said NOx absorbers.  
     
     
         5 . The emission reduction system of  claim 4 , wherein said NOx absorbers may be selectively regenerated.  
     
     
         6 . The emission reduction system of  claim 4 , further comprising a diesel fuel reductant injection system associated with said NOx absorbers, said reductant injection system capable of delivering reductant to said NOx absorbers for regeneration.  
     
     
         7 . The emission reduction system of  claim 1 , where said at least one NOx absorber includes at least two NOx absorbers coupled in parallel; and the emission reduction system further comprises at least one valve adapted for selectively isolating said NOx absorbers from the exhaust stream.  
     
     
         8 . The emission reduction system of  claim 1 , wherein the exhaust stream is cooled to a temperature for improved operation of said at least one NOx absorber.  
     
     
         9 . The emission reduction system of  claim 8 , wherein said temperature is from 250° to 450° C.  
     
     
         10 . The emission reduction system of  claim 1 , further comprising a heat source capable of heating the exhaust stream.  
     
     
         11 . The emission reduction system of  claim 10 , wherein said heat source includes a diesel fuel fired burner.  
     
     
         12 . The emission reduction system of  claim 10 , wherein said heat source is capable of heating the exhaust stream to a temperature for improved operation of said particulate filter.  
     
     
         13 . The emission reduction system of  claim 12 , wherein said temperature is at least 270° C.  
     
     
         14 . The emission reduction system of  claim 12 , wherein said heat source is capable of heating the exhaust stream to a temperature sufficient for incineration of a substantial portion of particulates trapped by said filter.  
     
     
         15 . The emission reduction system of  claim 10 , wherein said heat source is capable of heating the exhaust stream to temperature for improved operation of said NOx absorbers.  
     
     
         16 . The emission reduction system of  claim 15 , wherein said optimal temperature is from 250° to 450° C.  
     
     
         17 . The emission reduction system of  claim 10 , wherein said heat source is capable of periodically heating the exhaust stream sufficient to improve the capacity of said NOx absorbers, thereby releasing from said NOx absorbed substances attributable to diesel fuel sulfur content.  
     
     
         18 . The emission reduction system of  claim 10 , further comprising a computing device capable of monitoring exhaust stream temperatures at the input of said filter and at the input of said first absorber.  
     
     
         19 . The emission reduction system of  claim 18 , wherein said computing device is further capable of controlling said heat source to adjust said exhaust stream temperature at the input of said filter.  
     
     
         20 . The emission reduction system of  claim 18 , wherein said computing device is further capable of controlling said heat source to adjust said exhaust stream temperature at the input of said at least one NOx absorber.  
     
     
         21 . The emission reduction system of  claim 18 , wherein said computing device is further capable of controlling said heater exchanger to adjust said exhaust stream temperature at the input of said at least one NOx absorber.  
     
     
         22 . The emission reduction system of  claim 1 , wherein said heat exchanger further includes a bypass path having a valve for selectively controlling the flow of the exhaust stream through said bypass path.  
     
     
         23 . A method of controlling an exhaust emission reduction system for reducing exhaust stream emissions produced by a diesel engine, comprising the steps of: 
 (a) monitoring and controlling the temperature of the exhaust stream entering a particulate filter, thereby improving the operation of said particulate filter; and    (b) monitoring and controlling the temperature of the exhaust stream entering a catalytic absorber of NOx, thereby improving the operation of said NOx absorber.    
     
     
         24 . The method of  claim 21 , further comprising the step of: 
 (c) periodically adjusting the temperature of the exhaust stream entering said particulate filter sufficient to incinerate a substantial portion of particulates trapped by said particulate filter.    
     
     
         25 . The method of  claim 24 , wherein the emission temperature of step (c) is at least 350° C.  
     
     
         26 . The method of  claim 24 , wherein step (c) is completed when the differential pressure across said particulate filter is above a predetermined level.  
     
     
         27 . The method of  claim 23 , further comprising the step of: 
 (d) periodically adjusting the temperature of the exhaust stream entering said absorber sufficient to improve the capacity of said NOx absorber, thereby releasing from said NOx absorber absorbed substances attributed to diesel fuel sulfur content.    
     
     
         28 . The method of  claim 27 , wherein the emission temperature of step (d) is at least 500° C.  
     
     
         29 . The method of  claim 23 , wherein the exhaust stream temperature of step (a) is at least 270° C.  
     
     
         30 . The method of  claim 23 , wherein the exhaust stream temperature of step (b) is between 250° and 450° C.  
     
     
         31 . The method of claims  23 ,  24 , or  27 , wherein the diesel engine is adapted for powering a vehicle.  
     
     
         32 . A computing device for controlling an exhaust emission reduction system for reducing exhaust steam emissions produced by a diesel engine, the emission reduction system including a particulate filter, a catalytic absorber of NOx, and a thermal transfer system capable of adding heat to or removing heat from the exhaust stream, the computing device comprising a processor and software capable of: 
 monitoring the temperature of the exhaust stream entering the particulate filter;    controlling the thermal transfer system to adjust the temperature of the exhaust stream for improved operation of the particulate filter;    monitoring the temperature of the exhaust stream entering the absorber; and    controlling the thermal transfer system to adjust the temperature of the exhaust stream for improved operation of the absorber.    
     
     
         33 . The computing device of  claim 32 , wherein the thermal transfer system includes a heat source and a heat exchanger, and said processor and said software are further capable of controlling said heat source and said heat exchanger to adjust the temperature of the exhaust stream entering the particulate filter and the NOx absorber.  
     
     
         34 . The computing device of  claim 32 , wherein said processor and said software are further capable of: 
 monitoring the pressure differential across the particulate filter; and    controlling the thermal transfer system to periodically incinerate particulates trapped by the particulate filter.    
     
     
         35 . The computing device of  claim 32 , wherein said processor and said software are further capable of controlling the thermal transfer system to periodically adjust the temperature of the exhaust stream to improve the capacity of said NOx absorbers, thereby releasing from said NOx absorbers absorbed substances attributed to diesel fuel sulfur content.  
     
     
         36 . The computing device of claims  33 ,  34 , or  35 , wherein the diesel engine is adapted for powering a vehicle and said processor and said software are further capable of receiving engine operating parameters.