What is the primary function of a reflux drum in a fractionation column?

The primary function of a reflux drum in a fractionation column is to provide a surge capacity for the condensed overhead vapor and to separate the liquid reflux from the product. A fractionation column, also known as a distillation column, separates components of a liquid mixture based on their boiling points. The overhead vapor from the column is cooled and condensed in a condenser. The resulting liquid stream is then sent to a reflux drum, which is a horizontal or vertical vessel. The reflux drum serves two main purposes. First, it acts as a surge tank to provide a stable liquid supply for the reflux stream. The reflux is a portion of the condensed overhead liquid that is pumped back to the top of the column to improve separation efficiency. The reflux drum provides a constant and controlled flow of reflux, even if there are fluctuations in the overhead vapor flow rate. Second, the reflux drum allows for the separation of any non-condensable gases that may be present in the overhead vapor. These gases, such as nitrogen or residual hydrocarbons that didn't condense, are vented from the top of the reflux drum. The liquid in the drum is then split into two streams: the reflux stream, which is pumped back to the top of the column, and the product stream, which is sent to storage or further processing. The reflux drum ensures stable column operation, efficient separation, and proper product quality.