As fuels age, deposits can form which in turn can cause operational disturbances and failures. In project 778 "Investigation on avoiding high-molecular aging products in middle distillates with alternative blend components under technical conditions", experiments were carried out on deposit formation in long-term storage and in various test rigs. The aim was to break down the formation and constituents of deposits and to find approaches for prevention. With the aid of various analytical methods, both the deposits and the fuels were examined to determine changes in the fuel and the composition of the deposits.
Within the scope of the tests, two different deposit types were found in some unadditive FAME-containing fuel mixtures. One deposition type occurred during long-term storage at 8 °C for B20 and for B100 after a few months and could be identified as a by-product of FAME production. These deposits consisted mainly of saturated monoglycerides. At a room temperature of 20 °C the deposits dissolved again in the oil. The deposits were identified mainly by a combination of 2D-GC and NMR techniques. However, a different type of deposits was found in the test bench tests. These mainly consisted of oxygenated FAME, long-chain alkanes and, to a lesser extent, polyaromatics and FAME. However, the composition of the deposits does not yet allow any conclusions to be drawn about their formation. One theory is that the FAME components are deposited in deposits formed from polyaromatics and cause them to swell. This can also explain why no test stand failure occurred in pure FAME.
Research Report Published: Ageing Products in Middle Distillates with Alternative Blend Components
The deposits could be avoided during the 18-month storage period by the presence of small doses of additives. In the test stand, the low additive doses delayed the test stand failures and did not show any observable influence on the composition of the deposits found.
Research Agencies:
OWI Science for Fuels gGmbH affiliated Institute of the RWTH Aachen
ITMC Institute of Technical and Macromolecular Chemistry RWTH Aachen
The research report 778 was published in German and can be ordered from the DGMK.
The IGF project 18951 N of the Research Association DGMK was funded via the AiF as part of the programme for the promotion of Industrial Collective Research (IGF) by the Federal Ministry for Economic Affairs and Energy on the basis of a resolution of the German Bundestag.