What is reflux ratio and how does it affect distillation column performance?

Reflux ratio (R) is the ratio of liquid returned to the column as reflux to the distillate removed: R = L/D. Higher reflux improves separation (fewer stages needed) but increases energy consumption and column diameter. Minimum reflux requires infinite stages; total reflux requires no product withdrawal. Optimal reflux is typically 1.2-1.5 times minimum reflux, balancing capital (stages) and operating costs (energy).