Engine aftertreatment system with exhaust lambda control

Abstract

An aftertreatment device for reducing nitrogen oxides (NOx), particulate matter (PM), hydrocarbon (HC), and carbon monoxide (CO) generated by a compression-ignition (CI) engine. In this device, lean exhaust air generated in the CI engine is converted to rich exhaust air, and energy used for the conversion is recycled using an energy recovery device. The result rich exhaust air then pass through an oxidation catalyst, where NOx is reduced with CO and HC.

1 . An emission control apparatus for an engine comprising:
 at least one combustion device for converting lean exhaust air emitted from said engine into rich exhaust air;   at least one energy conversion device for recovering heat energy generated in said combustion devices;   a catalyst in which NOx in said rich exhaust air is reduced through reactions with hydrocarbon and carbon monoxide;   
     
     
         2 . The apparatus of  claim 1 , wherein said combustion device is a fuel burner that includes a combustion chamber and an ignition means. 
     
     
         3 . The apparatus of  claim 1 , wherein said combustion device is an oxidation catalyst. 
     
     
         4 . The apparatus of  claim 1 , wherein said energy recovery device includes a turbine. 
     
     
         5 . The apparatus of  claim 1 , further comprises at least one external hydrocarbon doser for controlling hydrocarbon concentration in exhaust air. 
     
     
         6 . The apparatus of  claim 1 , further comprises at least one heat exchanger. 
     
     
         7 . The apparatus of  claim 1 , wherein said catalyst further includes lean NOx trap. 
     
     
         8 . An emission control apparatus for an engine comprising:
 at least one oxygen sorption device for converting lean exhaust air emitted from said engine into rich exhaust air;   a catalyst in which NOx in said rich exhaust air is reduced through reactions with hydrocarbon and carbon monoxide;   
     
     
         9 . The apparatus of  claim 8 , further comprises at least one external hydrocarbon doser for controlling hydrocarbon concentration in exhaust air. 
     
     
         10 . The apparatus of  claim 8 , wherein said oxygen sorption device includes at least two sections. Oxygen sorption materials in these sections work sequentially in removing oxygen in exhaust air. 
     
     
         11 . The apparatus of  claim 10 , wherein said sections include a working section and a regeneration section. Oxygen sorption material in the regeneration section uses rich exhaust air generated from the working section. 
     
     
         12 . The apparatus of  claim 8 , wherein perovskite-related oxides are included as an oxygen sorption material in said oxygen sorption device. 
     
     
         13 . The apparatus of  claim 8 , wherein said catalyst further includes lean NOx trap. 
     
     
         14 . A method of controlling exhaust emission of an engine, wherein the control system has an oxygen concentration control device, a catalyst facilitating reactions of NOx with HC and CO, and a dosing means providing HC, comprising:
 converting lean exhaust air into rich exhaust air by using said oxygen concentration control device;   controlling exhaust air temperature to a level appropriate for the reactions of NOx with HC and CO in said catalyst;   controlling HC level in exhaust air by using said dosing means to a level appropriate for reducing NOx in exhaust air.   
     
     
         15 . The method of  claim 14 , wherein said control system further includes a heat energy recovery device. 
     
     
         16 . The method of  claim 15 , further includes recovering the heat energy generated in converting lean exhaust air into rich exhaust air through said energy recovery device; 
     
     
         17 . The method of  claim 14 , further includes controlling HC level in exhaust air to a level appropriate for using said catalyst to remove the oxygen left in the process converting lean exhaust air to rich exhaust air using said oxygen concentration control device. 
     
     
         18 . The method of  claim 17 , further includes controlling exhaust air temperature to a level appropriate for reactions between oxygen and HC. 
     
     
         19 . The method of  claim 14 , wherein said oxygen concentration control device includes at least two sections. 
     
     
         20 . The method of  claim 19 , further includes controlling said sections working sequentially.