Refinery profitability can be raised by several ways viz. processing of opportunity crudes with confidence, molecular management, eliminating quality give away, operational changes in processing units specially in hydrotreaters which could optimize hydrogen use, sweating assets to match upstream and downstream units capabilities, extensive use of advanced process control and data analytic, change of catalyst, solvent, etc. At times, out of box thinking to solve an unforeseen situation could help to sustain refinery operations especially when market margins are high based on seasons. Here are a few case studies dealt by professionals of AshPhil in the past.
1. Delayed Coking Unit (DCU) is a carbon rejection unit in a refinery specially when refinery wants to make zero / near zero fuel oil. Typically, in a complex refinery DCU capacity will be approximately 30% by vol of crude intake. In one of the designs of a fuels refinery, the capacity chosen for DCU was about 22% by vol. This acted as a show stopper as all rest of the unit could be debottlenecked by about 20 to 30%. Also, higher capability in Coker will help to change crude mix to upstream Crude and Vacuum unit. A typical swing in diet from light crudes to heavy crudes would imply a gain of ~ 2 $/bbl. A comprehensive study was undertaken on Coker unit which showed the possibility to raise Coker to Crude ratio as high as 27% vol. Findings of the study were then ratified by DCU licensor and modifications were implemented during one of the turn around
2. Cat feed hydrotreater is a common unit in most refineries these days to treat vacuum gas oil and heavy coker gas oil prior to being used as feed stock in Fluid Catalytic Cracking (FCC) unit. The capacity of the hydroprocessing unit was a serious bottleneck as it was limiting crude intake despite the fact the upstream crude distillation unit had the ability to make higher amount of vacuum gas oil. Licensor stated that their design was optimal and nothing can be done about. However, a close look at the unit operating window showed lots area to be trimmed and a few reactor internals to be modified when compared with best in class designs. Further, with advancements in catalyst, the intake of hydrotreater could be raised by about 34% boosting refining margin.