Heavy-duty vehicles

Heavy-duty vehicles using natural gas favor storing natural gas as LNG instead of CNG. LNG vehicles should have the same exhaust emissions as CNG vehicles except that LNG vehicles might also occasionally vent methane from the fuel storage system. If LNG vehicles are used regularly, no venting of methane is necessaiy. However, if an LNG vehicle is left idle for a week or more, it will need to start venting to prevent excessive pressure in the fuel tanks. 

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SCR for heavy-duty vehicles reduces NOx emissions by 80%, HC emissions by 90% and PM emissions by 40% in the EU test cycles, using current diesel fuel (<350 ppm sulphur) [27], Fleet tests with SCR technology show excellent NOx reduction performance for more than 500000 km of truck operation. This experience is based on over 6 000 000 km of accumulated commercial fleet operation [82], The combination of SCR with a pre-oxidation catalyst, a hydrolysis catalyst and an oxidation catalyst enables higher NOx reduction under low-load and low-temperature conditions [83],... 

Just a few words to explain that in EuroV is that the clean-up strategy adopted by heavy-duty vehicles differs from that chosen by passenger cars. The heavy-duty vehicles have decided to reduce the engine-out particles emission levels and to treat the NOx released in the exhaust line by adopting the SCR-NH3 system. 

The second DeNOx technology, the selective catalytic reduction with ammonia (SCR-NH3) commercially available in heavy-duty vehicles since 2006, seems to present an interesting potential in terms of efficiency, reliability, HC penalties, etc. 

The urea distribution network in Europe, around year 2006, would be limited to one distribution point for a 500 km radius area (heavy-duty vehicles compatibility - data to be checked and actualized), and would not allow a co-fueling strategy whose interests are the simultaneous fuel/urea filling up at the service-station and the minimization of the urea tank volume. Today, it is difficult to anticipate the consequences of EuroV. 

Presently the catalytic selective NOx reduction by ammonia is efficient and widespread through the world for stationary sources. The remarkable beneficial effect of 02 for the complete reduction of NO into nitrogen is usually observed between 200 and 400°C. However, such a technology is not applicable for mobile sources due to the toxicity of ammonia and vanadium, which composes the active phase in vanadia-titania-based catalysts. Main drawbacks related to storing and handling of ammonia as well as changes in the load composition with subsequent ammonia slip considerably affect the reliability of such a process. On the other hand, the use of urea for heavy-duty vehicles is of interest with the in situ formation of ammonia. 

As expected, major environmental indicators are affected positively by the introduction of hydrogen cars. Demand for gasoline drops by more than 13% until 2030, compared with BAU, and demand for diesel by about 2%. The difference is significant, as in this scenario only passenger cars are equipped with fuel cells and H2-ICE engines, but neither buses nor light-duty vehicles are expected to be equipped with fuel cells. This means only a small share of diesel fuel consumers is affected, i.e., diesel cars, while buses, light- and heavy-duty vehicles (LDV, HDV) continue to run on diesel. 

There has been a recent revival in interest in the use of ethanol-diesel fuel blends (E-diesel) in heavy-duty vehicles as a means to reduce petroleum dependency, increase renewable fuels use, and reduce vehicle emissions [27]. E-diesel blends containing 10-15% ethanol could be prepared via the use of additives. However, several fuel properties that are essential to the proper operation of a diesel engine are affected by the addition of ethanol to diesel fuel - in particular, blend stability, viscosity and lubricity, energy content and cetane number (increasing concentrations of ethanol in diesel lower the cetane number proportionately) [28]. Materials compatibility and corrosiveness are also important factors that need to be considered. 

Westerholm, R. and Li, H. A multivariate statistical analysis of fuel-related polycyclic aromatic hydrocarbon emissions from heavy-duty vehicles, Environ. Sci. TechnoL, 28(5) 965-972, 1994. 

Westerholm, R., and K. Egeback, Exhaust Emissions from Light-and Heavy-Duty Vehicles Chemical Composition, Impact of Exhaust after Treatment and Fuel Parameters, Environ. Health Perspect., /02(Suppl. 4), 13-23 (1994). 

ESC European stationary driving cycle (for heavy-duty vehicles)... 

Very few heavy-duty propane vehicles have been developed and put into use therefore, a database of knowledge about their performance characteristics does not exist. However, their characteristics should be similar to the relative differences between natural gas heavy-duty vehicles and their diesel engine counterparts. If this supposition holds true, heavy-duty propane vehicles should have similar or better power, the same or better driveability, and better cold-start performance compared to the same vehicle with a diesel engine. (Unlike light-duty vehicles, heavy-duty propane vehicles should have better cold-start performance compared to diesel engines because of the many cold-start challenges diesel engines face.)... 

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