Abstract: The effects of online cleaning on catalyst activity and reactor pressure drop by using catalytic cracking (FCC) light cycle oil (LCO), kerosene and FCC slurry was studied on a fixed-bed residue hydrotreating unit. Firstly, the residue hydrotreating unit in the middle stage of operation was cleaned online for 72 h by using LCO, the density, carbon residue value, sulfur mass fraction and metal content of the hydrotreated oil decreased significantly after cleaning, and the metal content could be kept at a low level for a long time. The pressure drop in fixed-bed reactor was simulated by raising the reaction temperature，and the unit was cleaned online by using kerosene and FCC slurry,respectively. When kerosene was used to clean the reactor, the pressure drop of the reactor would quickly rise again,while the pressure drop of the reactor did not rise after 500 h of operation by using FCC slurry.It was concluded that the increase of pressure drop caused by coking of catalyst could be solved by intermittent cleaning of high aromatic FCC slurry.

Key words: residue hydrocracking, catalytic cracking lighe cycle oil, slurry, online cleaning, reactor, pressure drop