There are three different distillation methods that are used in crude oil refineries, and those are True Boiling Point Distillation (TBP), ASTM Distillation (ASTM), and Equilibrium Flash Vaporization (EFV). Each of these processes vary in the way distillation is achieved, so some methods are more effective than others.

True Boiling Point Distillation (TBP) is the most ideal process. It is a batch distillation operation which utilizes over 100 theoretical plates and a high reflux ratio of 100. This high number of plates along with a high reflux ratio allows for the best possible separation in distillation processes. These parameters also yield a pure compound since the temperature remains constant during evaporation of the unwanted compound.

The next method is ASTM Distillation. This process also uses a batch operation, but it does not include contact plates and it therefore has a reflux ratio of 0. Reflux inside the fractionation column flows downwards and cools vapors flowing upwards. The more reflux provided for a given number of plates results in more effective distillation, which is why this process is not as good as TBP.

The third distillation method is Equilibrium Flash Vaporization (EFV). This method is known yield the lowest degree of separation out of the three. EFV involves separation of the liquid and vapor in a flash drum after heating the flowing feedstock.