METHOD OF TRANSPORTATION OF LIQUEFIED NATURAL GAS Russian patent published in 2004 - IPC

FIELD: pipe line transport. SUBSTANCE: proposed method includes delivery of gas to pipe line at inlet pressure exceeding outlet pressure and reduction of gas temperature due to Joule-Thomson effect caused by drop of pressure in pipe line; inlet pressure is controlled for obtaining required outlet pressure; gas escaping from pipe line is liquefied for obtaining temperature of about minus 112 C and pressure sufficient for keeping the liquid at temperature below point of beginning of its boiling; liquefied natural gas is additionally transported in suitable container. Proposed method of transportation of liquefied natural gas includes the following stages: (a) at least part of flow of methanol-rich gas is cooled by passing this part through at least one heat exchanger cooled by means of closed-cycle refrigerating plant; (b) flow is additionally cooled due to its expansion in pipe line at reduction of pressure; (c) gas cooled during stage (b) is liquefied in liquefying unit for obtaining liquefied gas at temperature about minus 112 C and pressure sufficient for keeping the liquid at temperature at point below beginning of its boiling. According to second version, flow of gas at temperature of about minus 29 C to minus 73 C and pressure approximately of 1380 kPa to 6895 kPa is subjected to the following procedures: (a) flow of natural gas under pressure is introduced into first phase separation plant for forming first flow of liquid and first flow of vapor; 9b) pressure of liquid flow is controlled for obtaining pressure which is approximately equal to working pressure of third phase separation plant for separation phases in operation 91); (c) flow of liquid at regulated pressure is fed to third phase separation unit; (d) first flow of vapor is passed through first heat exchanger for heating first flow of vapor; (e) first flow of gas is compressed and cooled; (f) compressed first flow of vapor is passed through first heat exchanger for additional cooling of first flow of vapor; (g) compressed flow of vapor is passed through second heat exchanger for additional cooling of first flow of vapor at higher degree; (h) flow of vapor of procedure (g) is expanded reduction of pressure and temperature; (i) expanded flow is fed to second phase separation unit for forming second flow of vapor and second flow of liquid; (j) second flow of vapor is returned to first phase separation unit for repeated treatment; (k) second flow of liquid is expanded for additional reduction of pressure and temperature; (l) second flow of liquid is fed to third phase separation unit for forming third flow of vapor and flow of liquid product at temperature above minus 112 C and pressure sufficient for keeping the liquid at or below temperature of beginning of its boiling; (m) third flow of vapor is passed through second heat exchanger for cooling; (n) third flow of vapor is passed through third heat exchanger and is compressed to obtain pressure which is approximately equal to working pressure of first phase separation unit; compressed third flow of vapor is cooled and is passed through third heat exchanger, after which it is fed to first phase separation unit for repeated treatment. EFFECT: enhanced efficiency. 20 cl, 2 dwg, 2 tbl