The main recovery methods are adsorption, oil absorption and condensation separation. The principle of adsorption method is similar to that of molecular sieve double tower adsorption dehydration process; Oil absorption method is a method to separate different hydrocarbon gases based on the difference of solubility of each component in the absorbed oil; The condensation separation method is a method which uses the characteristics of different condensation temperatures of hydrocarbon components in natural gas to cool the natural gas to a certain temperature by refrigeration, so as to condense and separate the hydrocarbon with higher boiling point, and fractionate the condensate into qualified products. Refrigeration refers to the use of artificial methods to create low temperature (lower than the temperature of the environment) technology. Refrigeration system is closely connected with natural gas industry, mainly used for light hydrocarbon recovery, hydrocarbon dew point control, liquefied natural gas (LNG) and natural gas helium extraction, CO2 separation and other processes. At present, vapor compression refrigeration, throttling expansion refrigeration, expander refrigeration, heat separator refrigeration and gas vortex refrigeration are commonly used in light hydrocarbon recovery process. Oil absorption method can be divided into normal temperature oil absorption method and cold oil absorption method according to different absorption operating temperature. The operating temperature of normal temperature absorption method is normal temperature or slightly lower than normal temperature, which is mostly used in small and medium-sized units, with the main purpose of recovering C3+. The cold oil absorption method is a combination of oil and refrigeration. It can recover more C2+ Light Hydrocarbons by freezing the treated gas and absorption cold oil to 0~40 ℃. The recovery rate of C3+ can reach 85%~ 90%. It is commonly used in large-scale natural gas processing plants. According to the composition of natural gas and the degree of recovery of liquid hydrocarbon, condensation separation can be divided into shallow cold separation, deep cold separation and intermediate cold separation. The main purpose of shallow cooling separation is to recover propane (C3), and the refrigeration temperature is generally 15~-25 ℃; For the purpose of recovering ethane (C2) in cryogenic separation, the propane recovery rate should be more than 90% and the refrigeration temperature should be from - 90℃ to -100 ℃; The temperature of intercooling separation is generally - 30 ~- 60℃. Sometimes the intercooling separation is classified as the cryogenic separation part, which is collectively called the intercooling separation process.