Investigation on steam injection condition in refining vacuum furnace

•Injecting steam inside the radiant section is superior to the entrance.•The optimal steam injection location is at the oil bubble point area.•Excessive steam brings no benefits but unnecessary pressure drop.•Heavy crude process and deep-cut operation need earlier and more steam injection.

As worldwide petroleum reserves evolve toward heavier crude oils, crude distillation units encounter historically high coking risk, and this problem is further exacerbated by cutting deeper into the bottom for higher HVGO yield. In this work, we aimed to optimize the steam injection condition for coking prevention purpose in refining vacuum furnace. A new technology that injecting steam inside the radiant section was proposed and comparison was made with steam injection at the entrance. Variable steam injection location and rate were examined according different operating cases, and the flow patterns in vaporizing tubes and coking tendency curves were present. All the calculations were performed using the commercial software Petro-SIM and the calculation model was validated against on-site data. The criterion was proposed for the optimal steam injection condition. The results showed that steam injection inside the radiant section was superior to the entrance.