Natural gas liquids are certain chemical compounds that can be obtained in liquid form from natural gas. These compounds rank among the world’s most valuable energy resources. Natural gas liquids, also called NGL, are widely used as fuel, and in manufacturing petrochemicals and other products.
The chief NGL compounds, in order of increasing mass of their molecules, are ethane, propane, butane, pentane, hexane, and heptane. A molecule’s mass is the amount of matter it contains. Chemical manufacturers use ethane in making ethylene, an important petrochemical. Butane and propane, and mixtures of the two, are classified as LPG (liquefied petroleum gas). LPG is used chiefly as a heating fuel in industry and homes. Pentane, hexane, and heptane are called natural gasoline or condensate. Refiners blend natural gasoline with other gasoline.
Natural gas liquids are classified as light hydrocarbons. Hydrocarbons are a group of compounds containing only hydrogen and carbon. Natural gas is made up chiefly of hydrocarbons. All hydrocarbons become liquid under certain combinations of temperature and pressure, depending on the mass of their individual molecules. Light hydrocarbons liquefy at lower temperatures and higher pressures than do heavy hydrocarbons.
There are two main methods of producing NGL, condensation and absorption. In condensation, natural gas is chilled until it becomes a liquid from which the NGL are extracted. In absorption, processors mix gas with an oil that absorbs light hydrocarbons. NGL are then distilled from the oil. Natural gas processing plants produce most NGL.
