Fcc processing scheme with multiple risers

Abstract From the Canadian patent

F-3374, Abstract of the Disclosure, An FCC process wherein a fresh hydrocarbon feed of relatively poor crackability is mildly cracked in a first riser of a two riser system. Spent catalyst from the second riser is fed to the inlet of the first riser to produce relatively mild cracking conditions. A heavy fraction derived from the mildly cracked fresh feed is then vigorously cracked in the second riser to produce spent catalyst, and cracked product. Improved total gasoline plus distillate yields are achieved. The two riser system facilitates heat balancing the FCC process.