Reflux ratio of extractive distillation
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In extractive distillation, sometimes an excessively high reflux ratio results in lower purity of the light component; it is said that this is because the concentration of the extractant decreases, leading to a poorer separation effect. Does anyone have experience in carrying out such operations or in designing such processes?
Extractive distillation has strict requirements regarding the flow rates of the two phases. If the reflux ratio is too high, the increase in flow rate affects their distribution and their contact with the other phase, which in turn results in a poorer extraction efficiency. The flow rates must remain within the allowable range.
The backflow increases, which corresponds to a decrease in the solvent concentration on each tray; as a result, the selectivity of the solvent declines and the separation efficiency worsens
Extractive distillation relies on the selective effect of the extractant on the relative volatility; as the concentration decreases, this selective effect weakens, and as a result the relative volatility becomes closer to 1, which affects the separation efficiency