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Joined 2026-09-21 Message
Incoming links: Repeated ideal-stage enrichment
Fractional distillation 2026-10-18
Fractional distillation brings rising vapor into contact with descending liquid in a fractionating column. Packing supplies contact area; it does not act as a sieve for individual molecules. Repeated exchange can enrich the rising vapor in the more volatile component. Some condensed liquid returns downward as reflux, rather than all being withdrawn as distillate.[ref]
Distillation by Hong Kong University of Science and Technology. Introduction, paragraphs on reflux and plates, trays or packing
An equilibrium stage is an idealization of this contact. A real fractionating column has finite contact time and imperfect wetting and mixing; its length is not automatically a count of equilibrium stages. Product withdrawal and reflux affect the separation together. Thus the repeated ideal-stage enrichment example illustrates the composition advantage of repeated equilibration, but supplies neither a column design nor a specified reflux requirement.[ref]
Distillation efficiency. Hyper-TVT by ETH Zurich; §5.6 Efficiency, equilibrium versus actual plates and flow-dependent efficiency