EGR (Exhaust Gas Recirculation)

Exhaust gas recirculation routes part of the exhaust back into the scavenge air, lowering oxygen concentration and peak combustion temperature so that thermal NOx formation drops, the alternative to SCR for IMO Tier III. Marine EGR scrubs and cools the recirculated gas to protect the engine from sulfuric acid and soot. It is integral to the engine rather than an aftertreatment, and it carries a small fuel penalty from the reduced charge oxygen.