Natural gas produced from underground reservoirs must be process to remove water, impurities, and heavier hydrocarbons. The impurities are usually hydrogen sulfide and carbon dioxide. The heavier hydrocarbons or natural gas liquids (NGLs) are ethane (C2H6), propane (C3H8), butane (C4H10), and natural gasoline.

Natural gas liquids are recovered using four different technologies: refrigeration, cryogenic recovery, oil absorption, and dry-bed adsorption. Natural gas liquids are recovered by cooling or refrigerating the natural gas until the liquids are condensed out. The plants use Freon or propane to cool the gas.

Natural gas liquids are detached from the natural gas feed to recover the heavier hydrocarbons and to allow the treat gas to move through the pipeline network. The liquids are removed from the stream because they are more valuable (have higher prices) as raw materials to create chemicals and gasoline than they are as fuel. In addition the heavier liquids can condense out of the natural gas stream and cause problems in transporting the gas through pipelines.

Cryogenic recovery process are done at temperatures lower than -150 °F. The low temperatures allow the plant to recover over 90% of the ethane in the natural gas. Most new gas processing plants use cryogenic recuperation technology. Oil absorption is a process used by older gas processing plants and in many refinery gas plants.

This procedure is not as efficient as cryogenic processing and only 70% propane and all of the butane and natural gasoline are improved. Dry-bed adsorption is used to remove water and some of the natural gas liquids from the natural gas. The liquids are adsorbed on the surface of the desiccant such as silica gel. Desiccants are added to many products, such as medicine, to keep them dry. The adsorption process recovers 10 – 15% of the butane and 50 – 90% of the natural gasoline.