Application of deep-cut vacuum distillation process in atmospheric-vacuum distillation unit

The application of deep-cut vacuum distillation process in an 8.0 MM TPY atmospheric-vacuum distillation unit in SINOPEC Changling Petrochemical Company and design characteristics are introduced.The full-packing vacuum tower was installed in the unit and the tower was operated in micro wet conditions.The vacuum furnace diameter is expanded stage-wise,and oil flows to the vacuum tower through LP oil line.The high-efficiency steam evacuation system is provided at the top of vacuum tower using 1.0 MPa steam for evacuation.Over-vaporized oil is pumped to the inlet of vacuum furnace for recycle to improve the feedstock quality.In deep-cut operation,a high vacuum should be maintained at the overhead of the vacuum tower.The feedstock temperature is controlled at 390~395 ℃.A proper amount of steam is injected into the vacuum furnace,the temperature of vacuum tower bottom residue is controlled at 358~362 ℃ and the flowrate of scrubbing oil is controlled at 30~40 t/h.The factors affecting the deep-cut operation and solutions are summarized based upon the experience of two years' operation and analysis of operation data.