| abstract |
A dual riser FCC process is disclosed wherein first and second hydrocarbon feeds ( 5, 6 ) are supplied to the respective first and second risers ( 2, 4 ) to make an effluent rich in ethylene, propylene and/or aromatics. Where the hydrocarbon feeds are different, the respective risers can have different conditions to favor conversion to ethylene and/or propylene. A minor amount of a coke precursor ( 80, 82 ) can be added to one or both of the hydrocarbon feeds ( 5, 6 ) to reduce or eliminate the amount of supplemental fuel needed to heat balance the system. The different feeds, including the coke precursor and any recycle streams ( 36, 44 ) can be segregated by type to improve olefin yields, including an embodiment where the paraffinic feeds are supplied to one riser and the olefinic feeds to the other. |