Abstract: A converter for purifying exhaust gases from lean-burn engines, in particular for controlling the amount of NOx and soot from a diesel engine in transient operation such as a vehicle. The converter contains a catalyst bed with a catalyst effective for NOx reduction with a chemical reductant when the catalyst bed is with a certain temperature window and when the ratio between the molar amount of chemical reductant and NOx is above a certain minimum ratio. The catalyst bed is heated or cooled to a temperature within the temperature window and a switching valve is provided for reverse flowing the exhaust gases through the converter to maintain the catalyst bed at a temperature within the temperature window for a longer time than is possible with a conventional non-flow-reversing converter.

Abstract: The present invention relates to regenerative thermal or catalytic oxidizers and methods of operation thereof for oxidizing combustible components of feed gas mixtures. In accordance with the disclosed invention, operation of the heater used to supply supplemental heat to regenerative heat transfer oxidizers is controlled such that the input load to the heater is varied between a maximum input load and a nominal input load in response to a measured control temperature. The present invention provides improved temperature uniformity across the system for more efficient operation.