Influence of Fuel to Primary Exhaust Emissions and Secondary Aerosol Formation Potential from a Ship Engine

Particulate emissions from international shipping aren’t directly regulated, however the regulation for gaseous emissions (e.g. SOx, NOx) has been implemented in recent years. Also, limitations for shipping black carbon (BC) emissions are planned by IMO (International Maritime Organization). The aim of this study was to conduct a comprehensive characterization of gaseous and particulate emissions of a ship engine. Measurements were conducted at the VTT Technical Research Centre of Finland engine laboratory using a 1.6 MW Wärtsilä Vasa 4R32 LN medium-speed engine. Test fuels comprised fuels with 0.1%, 0.5% and 2.5% sulphur content and a biofuel blend. Two engine loads, 75% and 25% were used. Chemical composition of exhaust emissions was measured using a soot-particle aerosol mass spectrometer (SP-AMS). SPAMS enables the real-time measurements of particulate matter (PM) mass and size-resolved chemical composition of submicron non-refractory particulate matter, refractory BC and some metals and elements. In addition, in-depth chemical composition was analysed from filters. The secondary aerosol formation potential from exhaust emissions was studied using a potential aerosol mass (PAM) chamber. In addition, gaseous emissions, black carbon concentrations, size distributions of PM as well as physical properties of PM (e.g. volatility, hygroscopicity) were analysed using several state-of-the art online instruments. The main constituents of primary PM were BC, organic compounds and sulphates. Both fuel and engine load were observed to have a clear influence to both concentration and composition of the primary PM. Secondary aerosol was dominated by organic compounds and sulphur. The fuel was observed to have a large influence to secondary aerosol formation potential. Highest secondary aerosol formation potentials were observed for high sulphur (0.5-2.5% S) fuels