Study shows renewable diesel from crude tall oil is a high quality drop-in fuel for off-road engines
A team from the University of Vaasa (Finland) and UPM-Kymmene Corporation has examined how the blends of fossil and renewable diesel produced from crude tall oil (CTO) affect the performance and exhaust emissions of the modern common-rail off-road diesel engine.
The study, published in the journal Fuel, used four different fuel blends of low-sulfur fossil diesel fuel oil and CTO renewable fuel, UPM BioVerno (HB): HB10, HB20, HB50, and HB100. UPM BioVerno renewable diesel is produced from wood-based tall oil. (Earlier post.)
The suitability of this Finnish CTO renewable fuel has earlier been studied particularly in light-duty and passenger car vehicles. In the present study, CTO renewable diesel was investigated in a turbo-charged, intercooled common-rail non-road diesel engine. Considering the total demand of engine fuels and current supply of renewable fuels, it is realistic to concentrate on the blends of fossil and renewable fuels. In the present study, the renewable fuel was, however, also studied in neat form. As the baseline fossil fuel, regular low-sulfur Finnish DF was used.
The main aim of the present work was to study how different blends of the CTO renewable diesel (HB) in commercial low-sulfur diesel fuel oil (DF) affect the performance and exhaust emissions of a modern common-rail non-road diesel engine. Neat HB was also studied.—Niemi et al.
Crude tall is a natural extract of wood, mainly from conifers. The renewable raw material comes from sustainably managed forests. Crude tall oil is gained as a result of the separation process of fibrous material from wood; it is a residue of pulp manufacturing.
CTO is a mixture of 36–58% fatty acids, 10–42% of rosin acids and 10–38% sterols and neutral substances. However, its composition depends on tree species, time of the year, growing cycle and age of the tree, conditions of pulping, and the geographic location. CTO renewable diesel was produced via hydrotreatment in the UPM biorefinery in Lappeenranta.
Engine experiments were conducted by the University of Vaasa (UV) at the Internal Combustion Engine (ICE) laboratory of the Technobothnia Research Centre in Vaasa, Finland.
The study used an AGCO POWER 44 AWI turbocharged, intercooled, four-cylinder, common-rail diesel engine. The engine had been tuned for high NOx and the use of an SCR catalyst. No exhaust gas after-treatment system was, however, adopted for the current study—engine-out raw emissions were recorded during all measurements.
The team conducted performance and emission measurements according to the NRSC cycle of the ISO8178 standard. No engine or parameter modifications were made. Among the findings:
CTO renewable diesel showed performance and emissions results similar to those observed with GTL or BTL and oil- or fat-derived HVO fuels. NOx emissions were approximately constant—a slight discrepancy between the FT and HVO fuels that seemed to also show slight reductions in NOx. The authors noted that the fuel injection system of their present experimental engine was not at all optimized for the CTO fuel and its blends.
The cycle-averaged CO and HC emissions decreased when CTO renewable fuel content of the fuel blend increased. The main reasons were assumed to be the considerably lower content of aromatic compounds and the higher cetane number of the CTO renewable fuel.
The cycle-weighed NOx emissions remained almost constant independent of fuel.
Due to the high-NOx tuning, the exhaust smoke was very low, almost negligible for all fuels.
No coherent trend was observed in exhaust particle size distributions except at idle, where the increase in the HB content resulted in a clear reduction of ultra-fine particle number emissions. The peak number of particulates, however, tended to occur at slightly lower particle size category when the share of renewable fuel increased.
All in all, the studied CTO renewable diesel, UPM BioVerno proved to be a high quality drop-in fuel also for heavy-duty non-road diesel engines.—Niemi et al.
Seppo Niemi, Ville Vauhkonen, Sari Mannonen, Teemu Ovaska, Olav Nilsson, Katriina Sirviö, Sonja Heikkilä, Jukka Kiijärvi (2016) “Effects of wood-based renewable diesel fuel blends on the performance and emissions of a non-road diesel engine,” Fuel, Volume 186, Pages 1-10 doi: 10.1016/j.fuel.2016.08.048