Particle and Gaseous Emissions from Marine Engines Utilizing Various Fuels and Aftertreatment Systems

Shipping is facing major challenges with decarbonising targets (2050) and tightening emission regulations. SOx is already limited in the Emission Control Areas (ECA), and global limit for fuel sulphur content of 0.5 wt-% will apply in 2020. Tight Tier III NOx limits are applied for new builds in the NOx ECAs. So far, there is not explicit particulate matter (PM) emission limit, globally. However, there is a growing concern towards particle emissions and limits exist for PM in some special areas like inland waterways (in Europe) where also particle number (PN) emissions will be limited in 2020. In addition, IMO's work related to black carbon (BC) at the moment, anticipates BC limit coming in near future. Meeting the current and future limits will require careful consideration as many technologies are still developing and some are characterized by the short-term supply problems. Utilization of alternative fuels and after-treatment systems, like scrubbers and catalysts, is increasing. In present study, we have explored different emission reduction technologies for marine engines by experiments done onboard and engine laboratory. Various gaseous emissions, including e.g. SOx and NOx, and particle emissions, including PM, PN and BC, were studied. Measurements were done onboard two different ships, one being a modern cruising ship equipped with a selective catalytic reduction (SCR) and a hybrid scrubber, and the other one a RoPax ship equipped with a seawater scrubber. In addition, laboratory measurements were conducted with a medium speed marine engine using various fuels containing sulphur from 2.2% to below 0.1% and with a biofuel. Measurements were also done with natural gas as the main fuel in dual fuel mode. Different engine loadings representing both higher loads (typical operation at sea) and lower loads (typical at harbor areas) were studied. In this paper, we present the gaseous and particle emissions of the experiments done utilizing different fuels and after-treatment systems. We discuss the effectiveness of the relevant clean technologies (distillate fuels, biofuel, LNG, scrubber and SCR) to reduce emissions from marine engines.