Industry Definitions

Definitions of words and terms used in the gas processing industry.
For questions regarding incorrect/outdated entries or suggestion for adding additional terms, please contact Martin Erne

Hydrocarbon Component Fraction

A portion of mixture of hydrocarbons usually defined by boiling range such as naptha, gas oil, kerosene, etc.

Joule-Thomson effect

The change in gas temperature which occurs when the gas is expanded from a higher pressure to a lower pressure.

LNG (liquefied natural gas)

The light hydrocarbon portion of natural gas which has been liquefied.

LPG (liquefied petroleum gas)

Commercially available fuel products produced from gas processing, fractionation, and refining.

LTX unit (low temperature extraction unit)

A unit which uses the refrigerating effect of adiabatic expansion for improved liquid recovery from rich gas streams.


An acronym related to efficiencies.


A unit for measuring or expressing the volume of a million cubic feet of gas at standard conditions. The pressure and temperature conditions for the standard measurement must be defined.


A unit for measuring or expressing the volume of a thousand cubic feet of gas at standard conditions. The pressure and temperature conditions for the standard measurement must be defined.

NGL (natural gas liquids)

Hydrocarbons liquefied at the surface in field facilities or in gas processing plants.


A mechanical device that is used to move a fluid.

RVP (Reid Vapor Pressure)

A product specification for the heavier liquid products as determined by ASTM test procedure D-323.


Sedment and water contained in hydrocarbon liquid streams.

SNG (synthetic or substitute natural gas)

Methane and components produced by processes other than at a wellhead.

Wobbe number

A number proportional to the heat input to a burner at constant pressure. In British practice, it is the heating value of a gas divided by the square root of its gravity. Widely used in Europe, together with a measured or calculated flame speed, to determine interchangeability of fuel gases.


A fluid used to remove components from a gas stream by direct contact.


A tower or column that provides contact between natural gas, being processed and a liquid solvent.

absorption factor

A factor which is an indication of the tendency for a given gas phase component to be transferred to the liquid solvent. It is generally expressed as A = L/KV where L and V are the molar flows of liquid and vapor, and K is the average value of the vapor-liquid equilibrium constant for the component of concern.

absorption plant

A plant that processes natural gas with absorption oil, sometimes referred to as a "lean oil" plant.

absorption tower

Refer to definition of "absorber."

absorption-refrigeration cycle

A mechanical refrigeration system in which the refrigerant is absorbed by a suitable liquid or solid. The most common system uses ammonia as the refrigerant and water as the absorbing medium. Refer to definition of "compression refrigeration cycle."


A vessel used to facilitate the control of the flow of liquid or the separation of liquid from accompanying gas or vapor as the liquid flows through the plant for further processing.

acid gas

A gas stream that contains hydrogen sulfide and/or carbon dioxide.

adiabatic expansion

The expansion of a gas, vapor, or liquid stream from a higher pressure to a lower pressure in which the enthalpy of the stream does not change.


A solid substance used to remove components from natural gas being processed.


Removal of certain components from a gas stream onto a solid substance—including, but not limited to, one or more of the following: acid gases, water vapor, or heavier hydrocarbon vapors.