Objective At present, the distillation unit of the First Refinery Department in a petrochemical company owned by PetroChina (hereinafter referred to as "the independent refining") mainly processes three kinds of crude oils, namely, Kazakhstan crude oil, Karamay Mahu crude oil, and South Xinjiang Yaha crude oil. The unit adopts Shell decompression deep pull technology, which has been optimized continuously during the application. The refining process line is “hydrocracking cracking, catalytic cracking, delayed coking”, and the long-term implementation of the decompression deep pull operation is of great significance.

Method The unit was originally designed to be repaired every three years. Based on the continuous increase in crude oil weight, the cooling water volume and outlet temperature of the vacuum furnace were optimized to reduce the residual pressure at the top of the vacuum furnace. Measures were taken to solve the problems of excessive SO₂ emissions from the vacuum furnace flue gas and coking of the washing oil packing layer, so as to implement decompression deep pull.

Result Through optimized operations, the maintenance intervals of the unit have been extended to five years under reduced decompression deep pull conditions, reducing fuel gas consumption by 0.14 t/h and reducing residual oil yield by 0.61%.

Conclusion Long-term decompression deep pull have effectively reduced the production of low value-added coke, achieving significant economic benefits, which lay a good foundation for the overall operational efficiency of the company.