STRATEGIES FOR MAXIMIZING FCC LIGHTCYCLE OIL

摘要

Maximizing FCC Light Cycle Oil (LCO) yield to take advantage of high diesel prices relative torngasoline requires re-optimization of product cut point, operating conditions and catalystrntechnology. It is well known that LCO-to-gasoline ratio can be increased through loweringrnconversion by adjusting FCCU operating conditions and decreasing catalyst activity. [1,2] Therndrawback of this approach is the increase in bottoms yield. Recycle is often required to fullyrnmaximize LCO while maintaining bottoms yield consistent with a traditional maximum gasolinernoperation.rnIn this paper, we will provide a general discussion of strategies to maximize LCO in the FCCUrnand present laboratory results which quantify the effects of various recycle streams. A residrnfeedstock was cracked over a low Z/M MIDAS~? catalyst in Grace Davison's circulating riser pilotrnplant (DCR). The product bottoms was distilled to five recycle fractions (650-750℉, 650-800℉rn650-850℉, 650℉+ and 750℉+), blended back at various levels with the original feedstock andrncracked over a MIDAS catalyst in the ACE unit. Laboratory testing results were used to model arncommercial operation to demonstrate the yield advantage of selecting the appropriate recyclernstream, recycle ratio and catalyst technology.