The products of distillation are subjected to many other cracking, blending, and finishing processes before they are ready for use. How these downstream processes are operated depends largely on the crude oil that enters the atmospheric distillation column. The petroleum industry uses the differences in boiling points of the different compounds to extract the various fuels that we use in our every day lives. However, not all crude oil is the same. The percent of each boiling fraction in an individual crude oil differs widely, depending upon where the crude oil comes from.
Light crude tends to have more gasoline, naptha, and kerosene.
Heavy crudes will have more gas oil and heavy residues. Thus, for a given crude, there is a distillation curve that relates the boiling temperature of the compounds to the volume of the compounds available in each boiling fraction. The refinery engineer relies on this information to determine what the products of the atmospheric distillation column will be, and how to adjust conditions in other parts of the refinery. For example, a refinery must process a very heavy crude with a low volume of compounds in the gasoline boiling fraction range. This means that a larger share of heavy oils will be produced.