Primary Distillation Capacity
A distillation column separates crude oil into different petroleum products based on differences in boiling points this is called the Primary Distillation capacity. By itself, the crude distillation column has low yields of high-value transportation fuel products. Secondary Conversion Capacity
Many of the other chemical processes create products by either reshaping hydrocarbons, combining small hydrocarbons into larger hydrocarbons, cracking larger hydrocarbons into smaller higher-value hydrocarbons, or removing impurities such as sulfur. All of the units are the Secondary conversion capacity of the refinery. Each secondary processing unit after the distillation column has a specific purpose, whether it is increasing separation; upgrading low-value products, like residual fuel oil, to high-value products, like distillate; increasing octane; or enhancing environmental compliance by removing sulfur and other pollutants.