(1)   What is LNG? When natural gas is cooled to about - 162 ℃ under normal pressure, it changes from gaseous state to liquid state, which is called liquefied natural gas (LNG for short). (2) The main components of LPG are (propane and butane). (3) Acid gases in natural gas refer to (carbon dioxide and hydrogen sulfide).   (4) What are the necessary conditions for the design of natural gas liquefaction plant? Answer: plant design capacity (feed gas processing capacity or LNG output); Composition of feed gas; Product specifications; Site natural conditions; Utilities available on site; Equipment supply or EPC project; Technical service requirements.   （5) There are two main methods of natural gas dehydration (triethylene glycol method) and (molecular sieve method). (6) When deep dehydration is required, it should be removed by (molecular sieve method). (7) Briefly describe the purpose of natural gas light hydrocarbon recovery? Answer: in order to control the hydrocarbon dew point of natural gas to meet the requirements of natural gas transmission. The recovered liquid hydrocarbon products can be used as high-quality fuel or chemical raw materials, and have considerable economic benefits. (8) The Chinese names of NGL and LNG are (natural gas condensate) and (liquefied natural gas) respectively. (9) When the water dew point of natural gas is required to be lower than - 40 ℃, TEG shall be used for dehydration. (10) The purpose of CO2 removal in natural gas liquefaction unit is to prevent freezing and blocking at low temperature. (11)  What basic parameters need to be provided for the design of three-phase test separator skid? Answer: Inlet medium: components of crude oil, oilfield water and associated gas, physical properties (density, viscosity, etc.), sulfur content, sand content and sand particle size distribution Inlet medium temperature Inlet medium pressure Liquid phase treatment capacity: flow of crude oil and water Gas phase treatment capacity: natural gas flow (standard condition flow)