Abstract: In view of the current situation of poor economic benefits of diesel products, starting from the study on the properties of diesel and its narrow fractions of 4.0 Mt /a gas oil hydrocracking unit of Huizhou Petrochemical Company, it was found that the middle fraction of the diesel product was suitable for the production of No. 5 industrial white oil with better economic benefits. Therefore, the distillation system of the unit was simulated and evaluated, and the optimization measures were proposed and implemented, such as reducing the pressure of the main fractionation column to below 0.1 MPa and increasing the reboiler returning temperature of the diesel stripper. However, these measures based on existing facilities failed to raise the initial boiling point of diesel to the target value. In order to produce No.5 industrial white oil, the 220-360 ℃ fraction of diesel products was cut off and used as a raw material. Two techniques: (i) adding a steam stripper to the diesel side-line stripper flow,（ii）stopping the original reboiler of the diesel side-line stripper to use steam stripping, were proposed. The results showed that both proposals could increase the initial boiling point of diesel to 220 ℃ and produce the qualified No.5 industrial white oil. It is proved that revamping measures are helpful to turn diesel into white oil product with better economic benefits and improve the economic benefits of the whole plant.

Key words: hydrocracking, industrial white oil, fractionation column, process simulation