Abstract: The scale formation mechanism in slurry system of RFCC unit was introduced and analyzed. It is found the slurry scale is composed of catalyst, coke and metal compound and originates from deposition of catalyst, coking in transfer line, coking at the bottom of fractionator and slurry cycling with the coking in transfer line as the main reason. Stabilizing the operation conditions of RFCC will inhibit scale in transfer line from entering slurry system. Adding anti-scale agent in slurry is also an effective way to slow down scale formation.

Key words: slurry, coke, scale, RFCC