Assembly and method for reducing nitrogen oxides, carbon monoxide and hydrocarbons in exhausts of internal combustion engines

摘要

An assembly and method for reducing nitrogen oxides, carbon monoxide and hydrocarbons in exhausts of internal combustion engines, wherein the exhaust is acted upon in a first stage catalytic converter. A first portion of the first stage catalytic converter output is cooled and a second portion of the catalytic converter output is not cooled. The cooled and not cooled exhausts are united and directed to a second stage catalytic converter. Air is injected into a selected one of (1) the not cooled exhaust prior to the juncture thereof with the cooled exhaust, and (2) the combined cooled and not cooled exhausts after the juncture thereof.

主权项

1. A method of operating a catalytic system for reducing emissions from a rich burn spark-ignited engine, comprising:
controlling intake air and fuel (AFR) to produce first exhaust gases substantially free of oxygen; passing said first exhaust gases into a first-stage catalyst chamber containing a three-way catalyst (TWC), which minimizes NOx content by reducing NOx (to N2 and O2) to form second exhaust gases; cooling said second exhaust gases to 390-520° F.; increasing an oxygen content of said second exhaust gases to about 0.25-1.0%; passing said cooled exhaust gases into a second-stage catalyst chamber containing a catalyst that minimizes CO content by oxidizing CO to CO2.