TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: The cooling in step (b) is done by isenthalpic expansion, preferably isenthalpic expansion over an orifice or a valve, especially a Joule-Thomson valve or the cooling is done by nearly isentropic expansion, especially by means of an expander, preferably a turbo expander or a Laval nozzle, where the feed gas stream is pre-cooled to 15 to -35 degrees C, preferably 10 to -20 degrees C, before expansion. The cooling in step (d) is at least partly done by means of an external refrigerant, where the external refrigerant has a higher molecular weight than the gaseous phase rich in gaseous product to be cooled, preferably in which the external refrigerant comprises a propane cycle, an ethane/propane mixed refrigerant or an ethane/propane cascade. The gaseous phase rich in gaseous product is compressed before it is cooled in step (d). The gaseous phase rich in gaseous product is at least partly condensed into liquid phase contaminant, preferably in step (d) the gaseous phase rich in gaseous product is completely condensed into liquid phase contaminant. The feed gas stream has a temperature of -20 to 150 degrees C, preferably -10 to 70 degrees C, and a pressure of 10-150 bara, preferably 80-120 bara. The first temperature is -30 to -80 degrees C, preferably -40 to -65 degrees C and the pressure is 5-30 bara, preferably 10-20 bara. The second temperature is -50 to -80 degrees C, preferably -55 to -70 degrees C and pressure is 20-80 bara, preferably 30-60 bara. The third temperature is -40 to -100 degrees C, preferably -50 to -80 degrees C and pressure is 5-30 bara, preferably 10-25 bara. The third temperature is 1-50 degrees C lower than the second temperature. Preferred Components: The gas/liquid separator comprises a gas/liquid inlet at an intermediate level, a liquid outlet arranged below the gas/liquid inlet and a gas outlet arranged above the gas/liquid inlet, where normally horizontal coalescer is present above the gas/liquid inlet and a centrifugal liquid separator is arranged above the coalescer, both over the whole cross-section of the vessel. The liquid separator comprises at least one swirl tube. The gas/liquid separator comprises: a centrifugal separator containing bundle of parallel channels that are arranged within a spinning tube parallel to an axis of the rotating spinning tube; a housing with a gas inlet for contaminated gas at one end of the vessel; a separating body; a gas outlet for purified gas at the opposite end of the housing; and a contaminant outlet downstream of the separating body or upstream and downstream of the separating body. The separating body comprises many ducts over a part of the length of the axis of housing, where ducts have been arranged around a central axis of rotation. The separating body is composed of many perforated discs, where the perforations of the discs form the ducts.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The gaseous contaminants are carbon dioxide (10-90, preferably 5-80 vol.%) and/or hydrogen sulfide (0.1-60, preferably 20-40 vol.%). The feed gas stream is a natural gas comprising 20-80 vol.% of methane. EXAMPLE - No suitable example given.