Apparatus and method for controlling noxious components in automotive emissions using a conditioning catalyst for removing hydrogen

摘要

The invention relates to an improved emission control system. The system has particular applicability for use in an internal combustion engine (10) utilizing alternative fuels such as natural gas. More particularly, the invention provides an apparatus and method wherein hydrogen is removed by a conditioning catalyst (16) from the exhaust gas stream (21) to produce a conditioned exhaust gas (22). An exhaust gas oxygen (EGO) sensor (18) is in communication with the conditioned exhaust gas (22) and generates a signal in response to the sensed oxygen concentration of the conditioned exhaust gas (22). The A/F mixture entering engine (10) is adjusted by closed loop control means (14) in response to the signal generated by EGO sensor (18). The removal of hydrogen from the exhaust gas stream (21) eliminates lean shifts and allows oxygen sensor (18) and closed loop control means (14) to more accurately control the A/F ratio. As a result of improved control over the A/F mixture entering engine (10), main three-way catalyst (20) optimally converts noxious components present in the conditioned exhaust gas (22) to produce a purified exhaust stream (23).