what is reflux ratio

Reflux ratio is a term used in distillation, which is the most widely-used method of separating fluid mixtures on a commercial scale. Reflux ratio is defined as the ratio of the amount of the liquid fed back to the column as reflux to the amount of liquid withdrawn as distillate. In other words, it is the ratio between the boil-up rate and the take-off rate. The higher the reflux ratio, the more vapor/liquid contact can occur in the distillation column, which usually means higher purity of the distillate. However, it also means that the collection rate for the distillate will be slower. The reflux ratio can assume any number between a minimum value and an infinite value, and the number of theoretical stages required for separation changes with the reflux ratio. The optimum reflux ratio usually lies in the range of 1.1 to 1.5 times the minimum reflux ratio.