Page 40 - Fluid Catalytic Cracking Handbook

Process Description 23

Figure 1-13. A typical FCC main fractionator circuit.

The heaviest bottoms product from the main column is commonly
called slurry or decant oil. (In this book, these terms are used inter-
changeably.) The decant oil is often used as a "cutter stock" with
vacuum bottoms to make No. 6 fuel oil. High-quality decant oil (low
sulfur, low metals, low ash) can be used for carbon black feedstocks.
Early FCC units had soft catalyst and inefficient cyclones with
substantial carryover of catalyst to the main column where it was
absorbed in the bottoms. Those FCC units controlled catalyst losses
two ways. First, they used high recycle rates to return slurry to the
reactor. Second, the slurry product was routed through slurry settlers.