Hydrocarbon dew point

The hydrocarbon dew point is the temperature (at a given pressure) at which the hydrocarbon components of any hydrocarbon-rich gas mixture, such as natural gas, will start to condense out of the gaseous phase. It is often also referred to as the HDP or the HCDP. The maximum temperature and the pressure at which such condensation takes place is called the cricondentherm. The hydrocarbon dew point is a function of the gas composition as well as the pressure.

The hydrocarbon dew point is universally used in the natural gas industry as an important quality parameter, stipulated in contractual specifications and enforced throughout the natural gas supply train, from producers through processing, transmission and distribution companies to final end users.

The hydrocarbon dew point of a gas is a different concept from the water dewpoint, the latter being the temperature (at a given pressure) at which water vapor present in a gas mixture will condense out of the gas.

In the United States, the hydrocarbon dew point is related to the term GPM which is the gallons of liquifiable hydrocarbons contained in 1000 cubic feet of natural gas at a stated temperature and pressure. When the liquifiable hydrocarbons are characterized as being ethane or higher molecular weight components, they are reported as GPM (C2+). Similarly, GPM (C3+) refers to propane or higher molecular weight components and GPM (C6+) refers to hexane and heavier molecular weight components.