In order to separate the NGLs into individual products, the stream passes through a series of distillation towers. Distillation is the process of purifying a liquid by successive evaporation and condensation. The key parameters are the cut points, the temperatures at which various distilling products are separated. The temperature at which a product begins to boil is called the initial boiling point (IBP) and the temperature at which it is 100% vapourized is the end point (EP), together these two cut points constitute the fraction, all the compounds that boil between two temperatures.
In the first distillation tower, the stream is heated to boiling point permitting the lightest NGL product, that which has the lowest boiling point, to boil off the top of the tower as a gas where it is then condensed into a purity liquid and routed to storage. For our purposes, this product is ethane. The remaining product is transferred to the next tower where it is again boiled allowing product at the next fraction to boil off the top while the remaining product remains at the bottom. This continues untill the mixture has been separated into its purity products.