Abstract: In recent years, a variety of technical breakthroughs have been carried out to solve the coking problem in FCC unit, and good results have been achieved. At present, coking problems in slurry circulation system, fractionator bottom and reaction oil and gas pipeline have been solved effectively, yet coking problems in the top of settler and cyclone separation system of settler have not been fundamentally solved, which affects the longterm operation of catalytic cracking unit. This paper takes the coking phenomenon and characteristics of the settler of a number of enterprises in the catalytic cracking unit as the research object. Combining with the coking mechanism of the settler and the modification and application of the coking prevention technology, it explores and tackles the key problems. This provides technical support and guidance for solving the coking problem of settlers, and it also provides help for the long-term operation of the catalytic cracking units.

Key words: catalytic cracking/FCC, settling vessel, coking