Depropanizers

Depropanizers are distillation columns used in hydrocarbon processing to separate propane from heavier hydrocarbons in C3+ natural gas liquids streams. They are a core unit in LPG recovery and in refinery gas processing, typically operated after a deethanizer to split the ethane and lighter components from the propane-rich stream. The feed to a depropanizer is a mixed C3+ liquid that contains propane along with butanes and heavier hydrocarbons. The overhead product is enriched in propane and is routed to storage or further processing, while the bottom product contains C4 and heavier components for stabilizers, further processing, or downstream separation such as a butane splitter.

A depropanizer operates as a standard distillation column, using a reboiler to supply heat and a condenser with reflux to refine the separation. The column can use trays or structured packing, and its design is guided by the relative volatility of propane versus heavier hydrocarbons, the feed composition, target propane purity, and the desired operating pressure. In practice, these columns are designed to manage low-to-moderate pressures and operate at temperatures that maintain propane in the liquid phase within the column while its vapor reaches the overhead. Materials of construction depend on process fluids and any acid gases present, with corrosion resistance and compatibility to hydrocarbons being primary concerns.

In industrial practice, depropanizers are essential for producing LPG-grade propane and for feeding downstream fractionation trains. They are widely used in natural gas liquids plants, gas processing facilities, and some refineries. Efficiency and energy use are managed through reflux optimization, heat integration with adjacent columns, and periodic maintenance to control fouling and tray or packing performance.