FIELD: oil and gas industry.
SUBSTANCE: invention can be applied for partial liquefaction in stage plants at gas distribution stations of main gas pipelines. The flow of natural gas is extracted from the main gas line at the gas distribution station, pre-dried, cleaned and sent to multi-flow heat exchanger. Then into lower stage evaporator of two-stage refrigeration machine, where natural gas is cooled to the temperature of its condensation beginning and at least partially condensed. Coolant of the lower and upper stages of refrigeration machine is circulated in the lower and upper stages of the refrigeration machine which are a pure chemical component or azeotropic mixture boiling at constant temperature in the evaporator of the lower stage and upper stage, respectively. After the lower stage evaporator, natural gas is expanded in expansion device and then fed into collector-separator. It is divided into a stream of liquefied natural gas withdrawn as a commercial product and a return flow of non-liquefied natural gas. The return flow is fed to the multi-flow heat exchanger as a natural gas cooling medium, after which it is discharged into distributing gas line to the gas distribution station. A portion of the lower stage coolant vapours distilled from the lower stage evaporator is sent to precool natural gas to the multi-flow heat exchanger. At the outlet of the lower stage evaporator, natural has temperature equal to the sum of boiling point of coolant and the temperature deficiency in the lower stage evaporator.
EFFECT: at increase of gas flow rate through gas distribution station in cold season, the value of natural gas supplied for liquefaction flow rate is increased with respect to flow rate providing maximum attainable natural gas liquefaction factor.
2 cl, 3 dwg, 1 tbl
