A method of liquefying natural gas via indirect heat exchange with a refrigerant, the method using first, second and third coil-wound heat exchanger sections each having a tube side and a shell side, the shell side of the first coil-wound heat exchanger section being separated from and at a different pressure from the shell side of the second and third coil-wound heat exchanger sections, the method comprising the steps of:
- (a) passing a first natural gas stream through and cooling the first natural gas stream in the tube side of the first or second coil-wound heat exchanger section to form a first precooled natural gas stream;
- (b) passing the first precooled natural gas stream through and further cooling and liquefying the first precooled natural gas stream in the tube side of the third coil-wound heat exchanger section to form a first liquefied natural gas stream;
- (c) combining, flashing and separating the first liquefied natural gas stream and a second liquefied natural gas stream to form a liquefied natural gas (LNG) product and one or more flash gas streams, said one or more flash gas streams comprising a first flash gas stream;
- (d) expanding a first gaseous stream of the refrigerant to form a first expanded gaseous refrigerant stream at a first pressure and a first temperature;
- (e) passing the first expanded gaseous refrigerant stream through and warming the first expanded gaseous refrigerant stream in the shell side of the first coil-wound heat exchanger section to form a first warmed gaseous refrigerant stream;
- (f) passing a second gaseous stream of the refrigerant through and cooling the second gaseous stream of the refrigerant in the tube side of the first coil-wound heat exchanger section to form a precooled second gaseous refrigerant stream;
- (g) passing a third gaseous stream of the refrigerant through and cooling the third gaseous stream of the refrigerant in the tube side of the second coil-wound heat exchanger section to form a precooled third gaseous refrigerant stream;
- (h) combining and expanding the precooled second and third gaseous refrigerant streams to form a second expanded gaseous refrigerant stream at a second pressure and a second temperature, wherein the second pressure is lower than the first pressure and the second temperature is lower than the first temperature;
- (i) passing the second expanded gaseous refrigerant stream through and warming the second expanded gaseous refrigerant stream in the shell-side of the third coil-wound heat exchanger section and then the shell-side of the second heat exchanger section to form a second warmed gaseous refrigerant stream;
- (i) dividing a natural gas feed stream to form the first natural gas stream and a second natural gas stream;
- (k) warming the first flash gas stream in a fourth heat exchanger section;
- (l) passing the second natural gas stream through and cooling and liquefying the second natural gas stream in the fourth heat exchanger section, via indirect heat exchange with the first flash gas stream, to form the second liquefied natural gas stream;
- (m) withdrawing a precooled portion of the second natural gas stream as a first natural gas side stream from an intermediate location of the fourth heat exchanger section;
- and
- (n) introducing the first natural gas side stream into the first precooled natural gas stream before carrying out step (b).