Propane De-asphalting – Solvent de-asphalting processes are a major part of refinery operations and are not often appreciated for the tasks for which they are used. In the solvent de-asphalting processes, an alkane is injected into the feedstock to disrupt the dispersion of components and causes the polar constituents to precipitate. Propane (or sometimes propane/butane mixtures) is extensively used for de-asphalting and produces a de-asphalted oil (DAO) and propane de-asphalted asphalt (PDA or PD tar). Propane has unique solvent properties; at lower temperatures [38-60°C (100-140°F)], paraffins are very soluble in propane and at higher temperatures [about 93°C (199°F)] all hydrocarbons are almost insoluble in propane.
Propane De-asphalting | Delayed Coking Process Overview
A solvent de-asphalting unit processes the residuum from the vacuum distillation unit and produces de-asphalted oil (DAO), used as feedstock for a fluid catalytic cracking unit, and the asphaltic residue (de-asphalter tar, de-asphalter bottoms) which, as a residual fraction, can only be used to produce asphalt or as a blend stock or Vis-breaker feed-stock for low-grade fuel oil.
Solvent De-asphalting Schematic
Solvent de-asphalting processes have not realized their maximum potential. With ongoing improvements in energy efficiency, such processes would display its effects in a combination with other processes. Solvent de-asphalting allows removal of sulfur and nitrogen compounds as well as metallic constituents by balancing yield with the desired feedstock properties.