Particle Emissions from Ships

Doctoral thesis, 2016

Since 1st of January 2015 ships operating in sulphur emission control areas (SECAs) have to use marine fuels with a fuel sulphur content less than 0.1 %m/m. This regulation forces the ship owners to make a fuel shift and use low-sulphur marine fuel oils, use alternative fuels or use scrubbers on-board their ships. One driving force behind the regulation of the fuel sulphur content was to reduce the emissions to air of harmful particles. This thesis focuses on the two first strategies and evaluate how fuel sulphur content and other fuel characteristics affect the particle emissions. This thesis presents results from particle measurements done in test-bed engine labs and on-board operating ships, with focus on number, mass and sizes of the emitted particles. The on-board measurements considered how a fuel shift from a heavy fuel oil to a low-sulphur residual marine fuel oil and how use of an alternative fuel, in this case liquefied natural gas (LNG) affect the particle emissions. In the test-bed engine measurements the particle emissions from different types of fuels and the effects of fuel sulphur content and other fuel characteristics, primarily the content of aromatics, were investigated. The results highlight that reduced fuel sulphur contents will not be the only solution for reducing particle emissions, and other fuel characteristics need to be considered. The fuel sulphur content influences the emissions of particles with a diameter of 50 nm or less, whereas other fuel characteristics affect particles in all sizes. An increased content of aromatics did not result in increasing particle emissions, which indicate that the content of aromatics may not play a crucial role with respect to particle emissions from ships. Furthermore, the fuel shift strategy and changing from heavy fuel oil to a low-sulphur residual marine fuel oil, did not affect the number of particles emitted significantly: similar amounts of number of particles were emitted and there was an increase in the emissions of smaller particles. In contrast, the strategy of using an alternative fuel, here LNG, resulted in significant reductions of the particle emissions. Furthermore, the results also highlight the importance of conducting measurements of number of particles emitted when studying particle emissions from ships and in any future regulation of these emissions.