a method for liquefying gas involving pre - treating the gas stream in a pre - treater to remove impurities , and then passing the gas stream through a first flow path of a first heat exchanger to lower a temperature of the gas stream . the gas stream is then passed through the gas expansion turbine to lower a pressure of the gas stream and further decrease the temperature of the gas stream . the gas stream is then passed into a primary separator to separate the gas stream into a liquid stream and a cold gas stream . the liquid stream is collected . selected quantities of the cold gas stream are passed through a second flow path of the first heat exchanger whereby a heat exchange takes place to cool the gas stream flowing through the first flow path to maintain the temperature of the gas stream entering the gas expansion turbine at a temperature which promotes the production of liquids .