The front end of a typical crude oil refinery is illustrated in the BFD shown below. Crude oil, after desalting, is sent to the main fractionating column which operates at a pressure of 1.5 - 2.0 bar....

340°c Atmospheric Residuum > 540°C Vacuum Residuum Main Fractionator Vacuum Column "/>
Extracted text: The front end of a typical crude oil refinery is illustrated in the BFD shown below. Crude oil, after desalting, is sent to the main fractionating column which operates at a pressure of 1.5 - 2.0 bar. Many side streams are taken from the column, each side stream or "cut" has a characteristic boiling point range. As we move toward the bottom, the cuts become heavier, and the corresponding boiling points of the streams become higher. The material that leaves the bottom of the 1. < 40°c="" main="" fractionator="" is="" called="" light="" gases="" atmospheric="" residuum.="" this="" stream="" is="" further="" treated="" in="" a="" second="" column="" that="" operates="" at="" a="" relatively="" high="" vacuum="" (top="" pressure="" may="" be="" as="" low="" as="" 0.027="" bar)="" why="" does="" this="" second="" column="" operates="" at="" such="" a="" low="" pressure?="" 40="" -195°c="" gasoline="" cut="" 195-275°c="" diesel="" cut="" crude="" oil="" 275-340°c="" desalter="" heavy="" gas="" oil="" vacuum="" gas="" oil="" 340-540°c=""> 340°c Atmospheric Residuum > 540°C Vacuum Residuum Main Fractionator Vacuum Column