Aromatic extraction, styrene extraction
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Why is vacuum applied directly after the overhead stream from the solvent recovery tower condenses in the reflux tank during aromatic extraction, whereas in styrene extraction, a subcooler is required before applying vacuum after the overhead stream condenses in the reflux tank?
You need to ask the process team about this… I guess that, with the same temperature of the incoming medium, styrene has a lower boiling point than aromatic hydrocarbons, so it vaporizes more easily and is carried away……
Personal opinion: Different material properties have different effects on the subsequent vacuum system. Aromatic extraction: The material is the product of hydrogenation; it contains no unsaturated hydrocarbons and has stable properties. Styrene extraction: The material is styrene, which tends to polymerize; its polymerization within the vacuum system can affect the long-term operation of the vacuum pump.
That’s more accurate – styrene volatilizes at low temperatures; it’s best to have a cryocooler before vacuuming to prevent as much of it from entering as possible.