Abstract: In response to changes in market demand, the straight-run diesel hydrocracking unit increases the production of refined diesel by increasing the processing volume. However, the mass fraction of sulfur of diesel fluctuates abnormally, and it could up to more than 200 μg/g. A series of reasons for the excessive sulfur content of diesel were investigated in detail, such as insufficient depth of refining reaction, internal leakage of heat exchangers, material interconnection, incomplete removal of hydrogen sulfide, sample impurity interference and so on. The results showed that the large changes in diesel flow rate led to the disturbance of ferrous sulfide FeS accumulated in the low point position of the pipeline, which in turn led to the excessive sulfur content of diesel. By adopting a series of control measures such as standard adjustment range of operating parameters and adding a set of diesel filters, it ensured that mass fraction of sulfur in diesel fuel was stable and qualified (< 3.2 μg/g), and the expected goal of increasing the production of refined diesel fuel was achieved.

Key words: diesel, sulfur content, internal leakage of heat exchanger, impurities, filter