Recent environmental concerns have led to calls for reduced hydrocarbon emissions to the atmosphere from a variety of sources. One source of emissions being examined in this regard is natural gas spot sampling methods that vent pipeline gases to the atmosphere. Some sampling techniques and equipment have been developed that do not emit greenhouse gases, but the need exists to test these methods for their ability to collect accurate, representative samples. Another related concern is the accuracy of samples drawn from streams near their hydrocarbon dew point (HDP). While the spot sampling methods...
Recent environmental concerns have led to calls for reduced hydrocarbon emissions to the atmosphere from a variety of sources. One source of emissions being examined in this regard is natural gas spot sampling methods that vent pipeline gases to the atmosphere. Some sampling techniques and equipment have been developed that do not emit greenhouse gases, but the need exists to test these methods for their ability to collect accurate, representative samples. Another related concern is the accuracy of samples drawn from streams near their hydrocarbon dew point (HDP). While the spot sampling methods recommended by current industry standards perform well on streams far above their HDP, little data are available on their performance near or at the HDP, where poor sampling methods can cause heavy hydrocarbons to condense from the sample and distort the analysis. This project evaluated the ability of four natural gas spot sampling methods, including two zero emissions sampling methods, to capture accurate, representative samples of gas streams at or near their hydrocarbon dew point (HDP). Two of the sampling methods tested were variations on the GPA fill-and-empty method, with additional steps intended to heat the sampling equipment above the HDP or clear condensed hydrocarbon liquids from the sample line. The other two sampling methods, which use the A+ Q2 sample cylinder and a constant-pressure floating-piston sample cylinder, were developed to prevent condensation of heavy hydrocarbons during the sampling process.