Gas Con Recovery and Stripping Issues at Turndown Conditions

In 2020 every refinery experienced rate reductions and changing economics. In the Marathon system every FCC unit was taken to minimum and the propylene recovery via the Absorber/Stripper system was maximized. Every unit handled this transition very well but one unit struggled. At minimum rates the unit experienced excessive H2S in the FCC naphtha, no flooding in the Absorber/Stripper system but flooding in the Debutanizer.

The troubleshooting effort included all the typical methods. The root of the problem was found by rating equipment at turndown conditions. The processing problem was a standard Absorber/Stripper problem but the root cause behind the issue was abnormal.