Nature of LNG a) Composition LNG / LCBM is a hydrocarbon mixture with methane as the main component, which contains a small amount of ethane, propane, nitrogen and other components usually existing in natural gas. Generally speaking, the methane content of LNG / LCBM is higher than 80% and the nitrogen content is lower than 3%. Although the main component of LNG is methane, the physical and chemical properties of LNG cannot be inferred from pure methane. The physical and thermodynamic properties of methane and other natural gas components can be found in relevant reference books and thermodynamic calculation manuals. b) Density The density of LNG / LCBM depends on its components, usually between 430kg / m3 and 470kg / m3, but in some cases it can be as high as 520kg / m3. Density is also a function of liquid temperature, and its variation gradient is about 1.35kg/m3. ℃.   Equips of LNG plant 1) Main process system main system composition of LNG / LCBM plant: Feed gas filtration and compression system  Feed gas deacidification system  Feed gas drying system Feed gas heavy hydrocarbon removal system  Mercury removal and filtration system of feed gas Purified gas low temperature liquefaction system LNG storage and transportation and bog compression system Main refrigeration system and / or auxiliary refrigeration system Safety relief system Instrument and electrical control system 2) Auxiliary system composition of LNG / LCBM plant auxiliary system: Circulating cooling water system Steam and / or hot water system Instrument air system Nitrogen system Fuel gas system or / and fuel oil system