8. Cat Cracking

Question 1

■ Objective and description of Cat Cracking process?
■ Supportive Processes?
■ Main Units?

Answer 1

■ Convert Fuel Oils heavy Gas Oils (Heavy oil. heavier than gasoline & naphta) into lighter fractions.
■ Contact with a catalyst at elevated temperatures and pressures.
■ 
▪ Cat Feed Heater (700ºF)
▪ Riser
▪ Disengagement chamber (900-1100ºF)
▪ Reactor
▪ Cyclone (centrifuge)
▪ Fractionator

Question 2

■ Feedstock (sources), output & disposition?

Answer 2

■ Feedstock:
▪ Heavy Gas Oil (Straight Run)
▪ Flasher Tops (Vacuum Flashing)
▪ Cycle Oil (Cat Cracking)
│
■ Output:
▪ C4 (Butane) and Lighter — cracked gas plant, sats gas plant, alkylation.
▪ CAT-Cracked Gasoline — motor gasoline blending component.
▪ CAT-Cracked Light Gas Oil — good component for distillate fuel (but not diesel fuel)
▪ CAT-Cracked Heavy Gas Oil — as a feed to hydrocracker or as a residual fuel component.
▪ Cycle Oil — recycled to extinction
▪ Coke

Question 3

■ Latitude in the cut point between?

Answer 3

■ There is quite a bit of latitude in
the cut point between:
▪ the gasoline and
▪ light gas oil stream.

■ Refiners use this as 
one way to regulate the balance between:
▪ gasoline and 
▪ distillate 
as the seasons change. 

As the winter heating oil season comes on,
many refineries go into a:
▪ max distillate mode.

They make adjustments to:
▪ the CCU fractionator to
▪ lower the end point of the cat-cracked gasoline to
▪ push more volume into the cat light gas oil.

In the summer, during a max:
▪ gasoline mode,
the shift is in the other direction.