Emission control in rich burn natural gas engines

摘要

A passive mid bed air injection apparatus for an engine includes a three way catalyst positioned in an exhaust stream of the engine. The three way catalyst reduces NO_x, CO and HC from the exhaust stream. The three way catalyst includes an ammonia slip catalyst positioned in the exhaust stream of the engine. The ammonia slip catalyst is positioned downstream from the three way catalyst and oxidizes NH₃ and CO from the exhaust stream. The three way catalyst includes an oxygen input disposed between the three way catalyst and the ammonia slip catalyst such that the oxygen input delivers air downstream from the three way catalyst and upstream from the ammonia slip catalyst. The oxygen input receives the air from a charged side of a forced induction device and delivers the air to the exhaust stream entering the ammonia slip catalyst. An associated method also provided.