Refineries are typically large-scale facilities that process crude oil to produce various products for commercial use. Crude oil is a mixture of many different hydrocarbon molecules of a range of sizes. Smaller molecules vaporize at lower temperatures, so crude oil can be distilled to separate out the different hydrocarbons. In the distillation process, crude oil is vaporized and the hot vapor rises up a column, cooling as it rises. Different hydrocarbons vaporize at different temperatures, so they condense into liquid form at different points in the column, separating the crude oil into different components that can then be further processed to optimize them for their final use.

The oil refining process is the central activity of downstream oil and gas companies. In the refining process, crude oil is refined to produce different petroleum products like gasoline, diesel, and jet fuel. For the conversion to take place, crude oil is heated and introduced into the distillation tower. In the tower, oil is broken down into various petroleum products.