The increased use of alternative liquid fuels to reduce greenhouse gas emissions poses challenges for many applications. To reduce greenhouse gas emissions, fossil fuels are being substituted by synthetic and biogenic fuels, leading to mixtures of different fuels on the one hand, but also to negative effects when using purely alternative fuels.
The heat generation used in the research project by evaporating middle distillates from a porous medium can result in deposits that impair operation or lead to a complete malfunction. In the predecessor project DGMK Project 767, the evaporation behavior on wetted hot surfaces and the occurrence of technical damage, e.g. due to chemical reactions (coking), were investigated.
In this research project, the use and influence of alternative fuels of biogenic and synthetic origin were investigated in addition to fossil fuels. Different fuel mixtures were used in fresh and aged condition. The fuels used were heating oil, diesel RME, HVO, GtL and 2-ethylexanol (alcohol). The deposit quantities produced in a test rig at the OWI were dependent on both the fuel (mixtures) themselves and the ageing condition of the fuel mixtures.
Further analysis of the deposit showed that coking appears to play a predominant role in deposit formation. 60 - 85 % of the deposits consist of inorganic carbon, while the remaining proportion consists mainly of pyrolyzable hydrocarbons with 0 - 3 oxygen atoms. Differences at the molecular level were found between deposits formed by different fuel mixtures. No specific marker compounds could be identified in the deposits; instead, an extremely complex, high-molecular mixture was formed.