Synthetic Fuels against Climate Change and Environmental Pollution

Authors

Dr. E. Jacob, Emissionskonzepte Motoren, Bodman-Ludwigshafen; 
I. Bogatykh, T. Goral, Dr.-Ing. P. Seidenspinner, Dr. T. Wilharm, ASG Analytik-Service GmbH, Neusäß;
A. Peter MSc, Dr. H. Scherer, Prof. Dr. I. Krossing, University of Freiburg

Year

2020

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 813

Summary

Apart from CO₂, the use of fossil fuels releases other environmental pollutants. With synthetic fuels, manufactured using sustainable electricity and CO₂, so-called E-fuels, climate protection can be combined with maintenance of a clean environment. Optimised E-fuels burn without forming PN₂₃ soot particles, and are liquid and suitable for thecurrent infrastructure. That is why the fuels OME_3-5 and DMC+ (a mixture of dimethylcarbonate, DMC, and methyl formate, MF) that can be made from methanol have provedto be the best choice for diesel or SI engines. In sunny areas, methanol can be producedfor energy costs below 2 €c/kWh, functions as an energy storage system and is easilytransportable worldwide. These second-generation E-fuels enable a significant reductionin the system complexity of the engine and exhaust gas treatment. Transport and storageof fuel become more secure. Since we do not expect the replacement of fossil fuels inthe foreseeable future, we investigate whether fuel additives with OME_3-5, DMC and MF can benefit the environment and the climate.
OME_3-5 are very ignitible (cetane number ≥70) diesel fuels that vaporise easily enabling high EGR rates with low exhaust emissions. The high flashpoint (≥60 °C) guarantees safety. New procedures have been developed for the analysis of impurities in OME_3-5. The formaldehyde content can be lowered to <2 mg/kg (blue grade OME^®). Standard DIN SPEC 51699 has been developed for the introduction of OME_3-5 in line with market requirements. The mixture of paraffinic diesel (first generation E-fuel) with OME_3-5 requires measures against phase separation in cold temperatures. A separation point (SP) is introduced as a characteristic value for the demixing temperature. The SP of HVO/OME 80/20 and 90/10 % (v/v) mixtures is 11 and -8 °C. A larger number of dissolving agents was checked for effectiveness. The lowest SP of HVO/OME 80/20 to date was detected at -6 °C and that of 90/10 % (v/v)- mixtures at -21 °C through the addition of 5 % 2-ethylhexanol.
With SI fuel, the high antiknock properties of DMC+ allow a downsizing of the engine with significantly higher efficiency levels. Blends with DMC and MF are only practical on the basis of paraffine-rich fuel with a final boiling point of 180 °C. The stabilisation of SI fuel-MF mixtures with additives is demonstrated.