Page 61 - Fluid Catalytic Cracking Handbook

Process Description 39

flows to a disulfide separator. A hydrocarbon solvent, such as naphtha,
washes the disulfide oils out of the regenerated caustic. The regen-
erated caustic is returned to the extractor and the solvent containing
disulfide oil is disposed in other units.

SUMMARY

Fluid catalytic cracking is one of the most important conversion
processes in a petroleum refinery. The process incorporates most
phases of chemical engineering fundamentals, such as fluidiza-
tlon, heat/mass transfer, and distillation. The heart of the process is
the reactor-regenerator, where most of the innovations have occurred
since 1942.
The FCC unit converts low-value, high-boiling feedstocks into
valuable products such as gasoline and diesel. The FCC is extremely
efficient with only about 5% of the feed used as fuel in the process.
Coke is deposited on the catalyst during the reaction and burned off
in the regenerator, supplying all the heat for the reaction.
Products from the reactor are recovered in the main fractionator and
the gas plant. The main fractionator recovers the heaviest products,
such as light cycle and decanted oil, from the gasoline and lighter
products. The gas plant separates the main fractionator overhead vapors
into gasoline, C 3's, C 4's and fuel gas. The products contain sulfur
compounds and need to be treated prior to being used. A combination
of amine and caustic solutions are employed to sweeten these products.

REFERENCES

1. Rader, Mari Lyn "Worldwide Refining," Oil & Gas Journal, December
23, 1996, p. 52.
2, Go, Tony, Baker Petrolite, Houston, TX, personal correspondence 1997.