Diesel Fuel

Abstract

Diesel fuel refers to the fuel that is used in compression-ignition engines (diesel engines). It is generally material boiling in the C 11 -C 22 hydrocarbon range. The requirements for diesel fuel are often diametrically opposed to that of motor-gasoline (Chapter 13). In motor-gasoline, it is important to suppress autoignition of the fuel to allow spark ignition to be correctly timed for good engine performance. In diesel fuel, it is important that the fuel autoignites and that the delay between fuel injection and the start of combustion is short.Compression-ignition engines operate at high compression ratios, typically around 15-17 : 1. This improves the thermodynamic efficiency of the engine, and on average compression-ignition engines are more efficient than spark-ignition engines. The engine itself is heavier, and traditionally it has been applied mainly for heavier vehicles. This situation has changed and, despite the higher cost of compression-ignition engines as compared to spark-ignition engines, there has been a marked shift in preference for diesel-powered passenger vehicles in Europe. This change is partly due to an increase in environmental awareness. Better engine efficiency leads to lower fuel consumption and can be translated into less CO 2 emitted per distance traveled. The move to vehicles with lower rated emissions (in grams of CO 2 per kilometer) is supported by the policies of the European Union.This shift in transportation fuel preference for the passenger vehicle market had a marked impact on refineries. The hydrogen in a typical conventional crude oil refinery is obtained from catalytic naphtha reforming. As the demand for motor-gasoline decreases, the need for reformate also decreases, which in turn reduces hydrogen production. Yet, refining crude oil to diesel fuel requires more hydrogen than refining crude oil to motor-gasoline. In each refinery there is a minimum motor-gasoline to diesel fuel ratio beyond which refining becomes inefficient and costly. The shift toward diesel fuel has created an imbalance in refinery production and in practice this imbalance in Europe is corrected by exporting motor-gasoline and importing diesel fuel. In the long run, it will be interesting to see how this might affect diesel fuel specifications, which over time have made diesel fuel production more difficult.Diesel fuel, like motor-gasoline, is a major consumer product and exerts a tremendous influence on the economy and the environment. Diesel fuel specifications are consequently subject to technical, environmental, and political pressures (Section 13.1).Fischer-Tropsch Refining, First Edition. Arno de Klerk.