Description
Lubricating oils are obtained from heavy oil cuts produced in vacuum distillation towers at refineries (lubricating oil base stocks). To produce lubricating oils, it is necessary to remove aromatics from the feedstock to a specified limit using a solvent. Oil cuts are composed of many complex compounds; therefore, to describe such processes, complex compounds are considered as pseudo-components. And the process simulation is performed using thermodynamic models. For the separation of aromatics from oil cuts in an RDC extraction column, a liquid-liquid extraction method is used. This paper, based on a research study conducted on the results of research presented in the field of simulating the process of extracting aromatics from oil cuts, examines this process.
Aromatic Extraction from Oil Cuts
Aromatic compounds exhibit a lower viscosity index, and their presence in oils diminishes the overall oil quality. To separate aromatics from oils, solvent extraction is employed. Solvents commonly used for extracting aromatics from oils include furfural, phenol, sulfur anhydride, N-methylpyrrolidine, and duosol. Increasing the solvent quantity in the process reduces the amount of refined material but enhances its quality.
Furfural is typically used as a solvent for aromatic extraction due to its favorable properties. The aromatic extraction unit consists of a tray column or one equipped with an agitator and a rotating plate. The feed and solvent enter the column from opposite sides and mix. A temperature gradient of 30 to 50 degrees Celsius is maintained from the top to the bottom of the extraction column, with a top temperature of approximately 140°C.
After the aromatic and oil phases separate, the oil phase is recirculated to the extraction column for further purification. Ultimately, after thorough purification, the oil enters the refinery’s dewaxing section. In this section, furfural is separated from the products through dissolution in water and distillation, and then recycled.
Simulation of Extraction of Aromatics from Oily Fractions
In this project, the unit for extracting aromatics from oily slices has been simulated with Aspen Hysys software. The extraction unit consists of a column with a tray or equipped with a rotary plate stirrer (RDC) ,The feed and solvent enter from the two ends of the column and move in the opposite direction and contact is established in this way and The ratio of solvent to feed and the temperature of the column is a function of the type of oil and the desired viscosity index. The figure below shows the process PFD.
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