The transportation industry is currently in a transition toward the use of
zero-emission vehicles; however, reaching it will take a considerable amount of
time. In the meantime, a diesel powertrain will remain the workhorse for most
heavy-duty transportation. In order to reduce the engine’s environmental impact,
biofuels, such as biodiesel, are used as drop-in fuels or fuel blends. The use
of drop-in fuels may create challenges for the fuel system since sticky deposits
can precipitate and cause injector malfunctioning or premature fuel filter
plugging. It has been concluded in the past that these deposits have been caused
by soft particles. In this article, soft particles created through the
degradation of biodiesel and their effect on filters are studied. The article
aims to analyze fuel filters and investigate the materials responsible for soft
particle separation. The study includes three pre filters and three main filters
that are commercially available truck filters. Different membrane types and
membranes with different pore sizes were tested in order to comprehend their
potential for fuel filtration. The tests were conducted using a custom-built
fuel filter rig, where pressure buildup was measured online. The removal
efficiency was assessed by gas chromatography-mass spectrometry (GC-MS) and
inductively coupled plasma (ICP). The materials of the filters were examined by
Fourier-transform infrared spectroscopy (FTIR), scanning electron
microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX), and thermogravimetric
analysis (TGA). The analysis revealed novel results from the interaction of soft
particles and different filter media. The filters show similar performance for
the commercial fuel filters with respect to soft particle removal and pressure
buildup and thus the tendency for fuel filter plugging, where the efficiency for
total calcium ion removal was around 40% for pre-filters and 60% for main
filters. The material analysis shows that the particles are most likely removed
mainly by the cellulose layer of the filter paper, and filters with glass fiber
showed higher capacity. In addition, the membrane filters prove to show good
potential for soft particle removal, with the highest removal of 72%; however,
their use in practice needs to be further evaluated in actual fuel systems.
