Aromatic extraction
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Can’t the rich solvent from the bottom of the extraction tower be sent directly to the recovery tower for the separation of aromatics and the poor solvent? Why is a stripping tower used in between, just to improve the purity of the aromatics?
The stripping tower is primarily used to separate aromatics from the solvent, while the recovery tower is used to recover the solvent further; the temperature and pressure in both towers need to be closely monitored
What manufacturing process is this? UOP consists of an extraction distillation column + a solvent recovery tower + a solvent regeneration tank
Liquid-liquid extraction and extractive distillation are somewhat different; in liquid-liquid extraction, a washing step is involved, so the distillation takes place in a stripping tower, whereas extractive distillation does not require this
I think it’s because it’s not easy to separate aromatic and non-aromatic compounds directly; the stripping tower is used to separate out the non-aromatic compounds
The non-aromatics are separated at the bottom of the stripping tower and sent to the recovery tower. Due to the low temperature in the extraction tower, it is only possible to separate most of the non-aromatics at higher concentrations of these compounds; there is a considerable amount of non-aromatics at the bottom of that tower. In the recovery tower, the solvent is obtained from the bottom, while everything else exits from the top. . .
The stripping tower is used to remove the small amount of non-aromatic compounds present in the solvent-rich mixture, thereby further increasing the purity of the aromatics. It works by stripping the non-aromatic compounds and a small amount of light aromatics from the tower; these substances are then used as backwash fluid and fed to the bottom of the extraction tower or as part of the extraction feed. Thanks to the selectivity of the solvent, the light aromatics displace the light non-aromatic compounds, which in turn displace the heavy non-aromatic compounds at the bottom of the extraction tower
You are experts in liquid-liquid extraction technology, right? The function of a liquid-liquid extraction stripping tower is to vaporize the small amount of non-aromatic compounds dissolved in the solvent from the top of the tower; this is not necessary in extractive distillation, as the non-aromatic compounds are already separated completely within the extractive distillation tower~