Mazda high vacuum ejector systems and hybrid ejector-liquid ring systems are installed in refineries Heavy crude from the atmospheric distillation columns is heated and fed to vacuum distillation columns, equipped with multistage ejectors, where it is fractionated into light oil, ethylene, phenol, caprolactam, amines and a variety of alcohols.
The residue from the atmospheric tower contains gas oils that are not recovered. The Crude Unit heater outlet temperature is limited due to the concerns over thermal cracking. Thus, the residue from the bottoms of the Atmospheric Distillation unit can be piped to another distillation column operated under vacuum , called a Vacuum Distillation unit (VDU), to recover additional heavy distillates. This allows the heavy hydrocarbons (boiling points >450oC) to be separated without the threat of partial thermal cracking into less desirable products such as coke. Since the boiling points of hydrocarbons are a function of pressure, the VDU can vaporize these components at a temperature lower than that at which thermal cracking will occur.