PTQ Q2 2023 Issue

duty because the bottom product total C 2=’ s are very low at only 300-400 ppm mol%. Once targeted C 2= composition is reached, any incremental duty above the minimum vapour- ises more C 3=, raising overhead vapour rate leaving the col - umn. The majority of the reboiler duty is sensible heat to raise the feed from 131°F to a bottom product temperature of 214°F. Column reboiler return and even internal column tray temperatures are a poor proxy for C 2= composition. Conclusion Increasing FCC reactor LPG yields at the expense of gaso- line increases profitability due to product differential values. However, equipment downstream of the converter requires modifications to handle higher WGFR, condense incremen - tal LPG, and recover it in the absorber/stripper system. Each FCC revamp depends on the existing unit constraints. 9 Key variables around the WGC system and absorber/stripper system can be manipulated to avoid major capital invest- ment. Detailed pressure surveys measuring individual pip- ing runs and equipment pressure drops allow potential modifications to be quickly established. The modifications identified can be used to narrow reactor yield cases that fit within capital constraints. Identifying and prioritising cost- effective opportunities during pre-conceptual and concep- tual project phases leads to well-defined project scope and successful project execution. References 1 Golden, S., Pulley, R., Dean, C., Catalyst changes, downstream im - provements increase FCC propylene yields, Oil and Gas Journal , Oct. 4, 2004. 2 Dean, C., Golden, S., Hanson, D., Understanding unit pressure bal- ance key to cost effective revamps, Oil and Gas Journal, May, 10, 2004. 3 Dean, C., Golden, S., FCC Reactor Line Coking, PTQ, Revamps and Operation , Autumn 2003. 4 Barletta, A., Golden, S., Centrifugal Compressor Operation, PTQ , Q2 2004. 5 Golden, S., Fulton, S., Hanson, D., Understanding Centrifugal Com- pressor Performance, PTQ , Spring 2002. 6 Golden, S., Fulton, S., Hanson, D., Understanding Centrifugal Com- pressor Performance in a Connected System, PTQ , Spring 2000. 7 Golden, S., Moore, J., Nigg, J., Optimize revamp projects with a logic- based approach, Hydrocarbon Processing , Sept 2003. 8 Langdon, D., Golden, S., Hartman, E., FCC Gas Concentration Unit Stripper Revamp, PTQ, Revamps 2007. 9 Whatley, M., Golden, S., and Barletta, A., Fast-tracking an FCC Re - vamp, P TQ, Revamps 2006. Darrell Campbell is a process engineer specialising in refinery revamps for over 15 years. He holds a degree in aerospace engineering from Texas A&M University and a PE in chemical engineering. Email: dcampbell@revamps.com Tony Barletta is Vice President of Process Consulting Services. He has over 35 years of experience with refinery revamps and process design for heavy oil units. Email: tbarletta@revamps.com Scott Golden is President of Process Consulting Services. He has more than 43 years of experience including refinery process design, refinery technical service, and distillation equipment design. Email: sgolden@revamps.com

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