重油
Refineries then execute processes that cause various physical and chemical changes in the crude oil and natural gas. This involves extremely specialized manufacturing processes. One of the important process is distillation, i.e., separation of heavy crude oil into lighter groups (called fractions) of hydrocarbons. There are two processes of distillation: CDU process and VDU process. The objective of the CDU process is to distill and separate valuable distillates (naphtha, kerosene, diesel) and atmospheric gas oil (AGO) from the crude feedstock. The technique used to carry out the above process is called complex distillation. On the other hand, the objective of the VDU process is to recover valuable gas oils from reduced crude via vacuum distillation. Two of the fractions of distillation are fuel oil and naphtha, which are familiar to consumers. Fuel oil, is used for heating for diesel fuel in automotive applications. Naphtha is used in gasoline and also used as the primary source for petrochemicals.