Technology

The Distapex^® process uses extractive distillation to recover individual aromatics from a heart-cut feedstock containing the desired aromatic compound.

The feedstock enters the extractive distillation column in its middle section while the solvent, N-methylpyrrolidone (NMP), is fed on the top tray of its extractive distillation section. The NMP solvent allows the separation of aromatic and non-aromatic components by enhancing their relative volatilities. Due to the low boiling point of the solvent only medium-pressure steam is required.

The vapors rising from the extractive distillation section consisting of non-aromatic components still contain small quantities of solvent. These solvent traces are separated in the raffinate section located above the extractive distillation section. The purified non-aromatics are withdrawn as overhead product.

The rich solvent comprising the aromatic component is withdrawn at the bottom of the column and sent to the solvent stripper column, in which the contained components are stripped off under vacuum conditions.

The aromatic stream is withdrawn as overhead product, while the stripped solvent is circulated back to the extractive distillation column. An optimized heat integration results in a very low consumption of medium-pressure steam. In contrast to competing technologies, solidification of the solvent during maintenance works will not occur due to the low solidification point of NMP.

The recovery rate is typically more than 99.5% depending on the aromatic content in the feedstock.

Source: Jack, 3rd Jun 2018, Aromatics Extractive Distillation Process, Oil & Gas Process Engineering