This article is about using reflux in chemical engineering and chemistry. For the reflux of stomach acids, see articles on heartburn, acid indigestion, and gastroesophageal reflux. For the reflux of urine, see vesicoureteral reflux. Reflux is a technique used in industrial and laboratory distillations. It is also used in chemistry to apply energy to reactions over a long time. Reflux in industrial distillation The term reflux is very widely used in industries that utilize large-scale distillation columns and fractionators such as petroleum refineries, petrochemical and chemical plants, and natural gas processing plants. In that context, reflux refers to the portion of the overhead liquid product from a distillation column or fractionator that is returned to the upper part of the column as shown in the schematic diagram of a typical industrial