Maximise VGO Yield
SUMMARY
Fundamental operating principles of vacuum ejectors are discussed, including incidents leading to sudden increases in ejector suction pressure, known as breakthrough. Proper ejector component selection and design can significantly prevent breakthrough and increase VGO yield, while reducing resid production.
TEXT
Good vacuum unit performance is critical with crude oil and asphalt price differentials as high as $20-25 per barrel. For a moderately sized vacuum unit, poor performance can easily increased vacuum residue production by 1000bpd, resulting in profit loss as high as $8-9MM/yr. Unreliable vacuum ejector system performance is often the root cause of the lost profits. Because ejector systems continue to be plagued with design problems during revamps, more effort needs to be directed at the proper selection and design of the system components. Avoiding these design mistakes begins with understanding fundamental operating principles.
Maintaining vacuum gas oil (VGO) product yield throughout the year requires minimum flash zone pressure and maximum temperature. Operating pressure and temperature determine gas oil product yield for a given feedstock quality assuming heater coil steam rate and stripping section performance are constant. Flash zone temperature is set by heater outlet temperature and pressure. Flash zone operating pressure is controlled by first stage ejector suction pressure...