Abstract: The application status of the third stage cyclone separator in FCC unit is introduced, and the main structures and existing problems of vertical multitube type third stage cyclone separator and horizontal multitube type third stage cyclone separator are expounded. And the main structures and advantages of BSX type third stage cyclone separator are presented. The BSX type third stage cyclone separator has been successfully applied in the FCC unit in one refinery. The industrial operation results showed that after using the BSX type third stage cyclone separator, the catalyst concentration in the outlet flue gas of the third stage cyclone separator was 90 mg/m³ (normal condition, the same below) and the large particle size (>10 μm) catalyst concentration was 1.52%(w). The overall separation efficiency of the BSX type third stage cyclone separator was 72%, and this indicated that the separation performance was excellent. The catalyst concentration and particle size in flue gas at the inlet of flue gas expander were far lower than the control index. The application of the BSX type third stage cyclone separator can provide good guarantee for the long-term safe and stable operation of flue gas expander.

Key words: catalytic cracking unit/FCCU, flue gas, BSX type, third stage cyclone separator, revamping