NOX Decomposition in Natural Gas, Diesel and Gasoline Engines for Selective NOX Recirculation

Selective NO_X Recirculation (SNR) involves three main steps in NO_X reduction. The first step adsorbs NO_X from the exhaust stream, followed by periodic desorption from the aftertreatment medium. The final step passes the desorbed NO_X gas into the intake air stream and feeds into the engine. A percentage of the NO_X is expected to be decomposed during the combustion process. The motivation for this research was to clarify the reduction of NO_X from large stationary engines.

The objective of this paper is to report the NO_X decomposition phenomenon during the combustion process from three test engines. The results will be used to develop an optimal system for the conversion of NO_X with a NO_X adsorbtion system. A 1993 Cummins L10G natural gas engine, a 1992 Detroit Diesel series 60 engine and a 13hp Honda gasoline engine were used in the experiments. Commercially available nitric oxide (NO) was injected into the engine intake to mimic the NO_X stream from the desorption process.

It was observed that the air/fuel ratio, injected NO quantity and engine operating points affected the NO_X decomposition rates. NO_X decomposition rates of 22% from the natural gas engine, 57% from the diesel engine and 87% from the gasoline engine were observed.