Demethanizer

A demethanizer is a distillation column used in natural gas processing to separate methane (C1) from ethane and heavier hydrocarbons (C2+). It is a key unit in gas processing trains that aim to deliver pipeline-quality gas while recovering natural gas liquids (NGLs). The column operates on the principle of volatility differences, using a reboiler to provide heat and a condenser to remove heat, establishing a methane-rich overhead and a C2+-rich bottom.

The feed to a demethanizer contains methane, ethane, propane and heavier components at elevated pressure. Through distillation, methane concentrates in the overhead stream, while ethane and heavier hydrocarbons exit from the bottom. The overhead product is typically treated as pipeline gas or used as fuel gas, whereas the bottom stream proceeds to further processing, such as stabilization, LPG recovery, or fractionation to separate ethane, propane, butane, and heavier fractions.

In many plants the demethanizer is part of a larger sequence that may include a de-ethanizer or other fractionation steps. The exact upstream arrangement varies, but the goal remains to maximize methane recovery in the overhead and to obtain a C2+-rich bottom stream for subsequent processing. Key operating variables include feed composition, column pressure, reflux ratio, and reboiler heat input, all adjusted to achieve the desired split between C1 and C2+.

Demethanizers are widely used in natural gas conditioning and LNG supply chains, contributing to gas quality specification and to the economic recovery of NGLs.