The Character of the Particle Emissions from Possible Future Marine Fuels in SOx ECAs

Licentiatavhandling, 2014

Particles in the ambient air come from both natural and anthropogenic sources. One anthropogenic source is combustion of fossil fuels. The awareness of these particles impact on human health and climate has increased the interest for the particle emissions from e.g. combustion of marine fuel oils during ship operations. The emissions contain particles of different sizes, with a major fraction of small particles, and particles of different composition, such as sulfate, organic matter and black carbon (BC). The size of the particles, i.e. diameter, is of interest in assessments of the impact of emissions on human health. There are up-coming international regulations on the sulfur content of marine fuel oils both at global level and in sulfur emission control areas (SOX ECAs) that probably will reduce the particle emissions from operating ships, due to a decrease of sulfate particles. Further, these regulations have increased the interest in the shipping sector in finding new fuel types to use. Until a few years ago, measurements of particle emissions from ships only resulted in data on mass of emitted particles. The increased understanding that size of particles is of importance has increased the interest for measurements of number of particles emitted and the sizes of them. The development of instrumentation that counts particles has made it possible to conduct these measurements as well. Possible future regulation of particle emissions from operating ships may include number of emitted particles, which requires a development of a standardized method for these types of measurements. The objective with this thesis is to characterize particle emissions from marine fuel oils with sulfur contents that comply with future regulations and from a possible future marine fuel, liquefied natural gas (LNG). The particle emissions from marine fuel oils were measured in a test-bed engine lab at Chalmers University of Technology and emissions from combustion of LNG were measured on-board a RoPax ferry operating in the Baltic Sea. The measurements have focused on the number of particles emitted. The results highlight that both sulfur content and fuel quality are important to consider in evaluating particle emissions from operating ships and that use of LNG will reduce the total amount of emitted particles, but a high fraction of the emitted particles will still be nanoparticles. The studies also highlight the importance of conducting measurements of the number of particles emitted when studying particle emissions from operating ships and in any future regulations of these emissions. Keywords: ship emission, emission factor, nanoparticle, marine fuel, liquefied natural gas, LNG, black carbon, heavy fuel oil, marine diesel oil