The invention discloses a method and device for double-stage expansion
refrigeration high
methane gas
liquefaction and belongs to the field of high
methane gas separation and
liquefaction. According to the purposes of the method and device for double-stage expansion
refrigeration high
methane gas
liquefaction, the problems of difficult heavy
hydrocarbon separation, cumbersome operation, high equipment investment, large methane loss and
high energy consumption in an existing production method for
liquefied natural gas are solved. The method comprises the steps of high
methane gas liquefaction and circulation
refrigeration. After high methane feed gas and preheating gas are mixed, the mixture is subjected to
heat exchanger cooling, throttling depressurization and gas-liquid separation, liquefied high
methane gas and low-temperature flashing steam are obtained; and the liquefied high
methane gas is collected as a product, and the low-temperature flashing steam is subjected to
open type circulation refrigeration or closed circulation. The method and device have the advantages of being simple in procedure, low in
energy consumption, flexible in operation, low in equipment investment, small in methane loss, good in
nitrogen separation effect, easy in heavy
hydrocarbon removal and the like.