Method for liquefying natural gas with improved exchanger configuration

A method for liquefying a hydrocarbon stream using at least one plate and fin heat exchanger comprising at least one first part and one second part, said first and second parts being physically separate and each comprising at least one stack of a plurality of plates that are parallel to one another and to a longitudinal direction that is vertical, the plates of the at least one first part and the plates of the at least one second part being stacked in a stacking direction that is orthogonal to the plates, said plates being stacked with spacing so as to define between them a plurality of first passages for a flow of at least part of a second two-phase cooling stream in the first part and a plurality of second passages for a flow of at least part of a first two-phase cooling stream in the second part, said method comprising:

• a) passing a hydrocarbon stream through the first part and the second part;
• b) introducing at least one cooling stream into the first part via at least one first inlet up to a first outlet, the at least one first inlet and the first outlet being arranged so that the at least one cooling stream flows through the first part in a downward direction opposite to the longitudinal direction;
• c) discharging the cooling stream introduced in step b) via the first outlet of the first part;
• d) introducing the cooling stream originating from step c) into the second part via a second inlet up to a second outlet of the second part;
• e) expanding the cooling stream originating from step d) so as to produce the first two-phase cooling stream;
• f) introducing at least part of the first two-phase cooling stream into the plurality of second passages of the second part via at least one third inlet up to a third outlet;
• g) discharging the first two-phase cooling stream via the third outlet so as to obtain the second two-phase cooling stream;
• h) introducing at least part of the second two-phase cooling stream into the first part via at least one fourth inlet of the first part up to a fourth outlet so that said second two-phase cooling stream flows in an upward direction following the longitudinal direction in the plurality of first passages;
• i) at least partially vaporizing said at least part of the first two-phase cooling stream in the plurality of second passages and said at least part of the second two-phase cooling stream in the plurality of first passages by exchanging heat with at least the hydrocarbon stream so as to produce an at least partially liquefied hydrocarbon stream at an outlet of the second part,
• wherein:
• the first part has a first fluid passage comprising a height and a width, and a cross-section defined as the product of the height and the multiplied by a number of the plurality of first passages of the first part;
• and
• the second part has a second fluid passage cross-section defined as the product between the height and the width of a second passage, multiplied by the number of the plurality of second passages of the second part,
• the heights of each of the passages being measured in the stacking direction and the widths of each of the passages being measured in a lateral direction that is orthogonal to the longitudinal direction and parallel to the plates,
• the second fluid passage cross-section of the second part being smaller than the first fluid passage cross-section of the first part.