FIELD: gas production industry.
SUBSTANCE: invention relates to methods of natural gas cooling and liquefaction. Fraction (A) rich in hydrocarbons is cooled in three areas (E1, E2, E3) of the heat exchanger with the help of a coolant. Coolant is compressed (C1) and then first part (4) of the flow is removed, which is expanded (X1) with performance of work. Remaining coolant flow (6) is cooled in the heat exchanger by itself to a temperature above the critical temperature of the coolant and is divided into second (8) and the third flow part (10). Second part (8) of the flow is expanded (X2) with performance of work, thus pressure and temperature are selected so that during expansion the liquid is not formed. Third part (10) of the flow is cooled by means of the expanded second part (9) of the flow and by means of itself so that during its further expansion (V1) the share of liquid is formed at least 90 mol. %. Third expanded two-phase portion (11) of the stream is evaporated in a heat exchanger and second portion (9) of the stream is mixed therewith. Refrigerant flow thus formed is heated in heat exchanger and the first flow part (5) is expanded to work thereon. Coolant flow is heated in heat exchanger before compression.
EFFECT: technical result is providing ratio of cooling capacity of two expanders (X1, X2) in range from 40/60 to 60/40.
3 cl, 1 dwg
