Model column overhead section choose a target reflux ratio estimate flows and duties see energy impact and convert between reflux and distillate rates built for process engineers students and operators with shareable results and unit aware inputs includes supports simple total condenser assumptions with latent heat entry provides helpful warnings on unrealistic values cases
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Distillation reflux is the portion of condensed overhead vapor that is returned to the column as liquid. The returning liquid flows down the rectifying section and contacts rising vapor, enriching the top with the more volatile component. Reflux ratio R is defined as L over D, where L is external reflux and D is distillate rate. When R increases, the operating line on a McCabe–Thiele diagram moves closer to the diagonal. That reduces the number of theoretical stages required for a given separation, but increases condenser duty and internal circulation. When R decreases toward the minimum reflux, separation becomes difficult and the required stages approach infinity. Practical design balances column height and energy use, typically choosing a ratio between 1.2 and 1.5 times the minimum value. In operation, reflux is adjusted to control overhead composition, recover from disturbances, or meet product specifications. A total condenser simplifies top balances, since V equals L plus D and R equals L divided by D. With partial condensers, definitions follow the external reflux stream. Because real columns deviate from ideal behavior, measurements should use consistent units and validated flowmeters, and calculations should state assumptions about latent heat, phase behavior, and side draws if present.
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