Straight-run distillation is the separation of crude into several fractions, each with its boiling point. Technically, this is achieved by heating the crude oil, then separating and condensing the vapors. The result is fuel distillates and the remaining heavy residue. The latter can be used in production of lube oil or in some chemical processes.
Straight distillation is performed in continuous systems, which allow to evaporate and fraction the distillates in a singe process loop. The refining column is separated by metal plates. The plates have orifices with covers. As the vapors ascend, they condense on the corresponding plate.
Gasoline vapor exits the column and must first be cooled by crude oil in a heat exchanger and only then by water in a refrigerator. Then gasoline vapor is condensed, part of that goes to storage, the rest is supplied to the column. Average gasoline yield is 3-15% of the crude oil by weight.
Among other products of straight distillation are kerosene, diesel fuel and solvent naphtha. These are also extracted from the column, cooled and stored. Heavy residue remain in the bottom of the column. It can be used to make oil distillates, but that process needs to run at 420-430ºС.
After extraction of oil distillates from the heavy oil, VTB remains. Highly viscous residue lube oil can be made form that by deep processing.