Patent WO-2021032916-A8 (WO)
Title: Method for liquefying natural gas with improved exchanger configuration
Inventor: HAIK-BERAUD NATACHA
IPC: F25J1/00
Filed: 2020-07-20
Abstract: The invention concerns a method for liquefying a hydrocarbon stream (102) such as natural gas, using at least one plate and fin heat exchanger comprising at least a first part (E2) and a second part (E2'), the first and second parts being physically separate and each comprising at least one stack of a plurality of plates (221, 222,...) that are parallel to one another and to a longitudinal direction (z) which is substantially vertical, the plates (221) of the first part (E2) and the plates (222) of the second part (E2') being stacked in a stacking direction (x) which is orthogonal to the plates (221, 222), the plates (221, 222) being stacked with spacing in such a way as to define between them a plurality of first passages (10) for the flow of at least a part of a second two-phase refrigerant stream (204) and a plurality of second passages (10') for the flow of at least a part of a first two-phase refrigerant stream (203) in the second part (E2'), the method comprising the following steps: passage of a hydrocarbon stream (102) in the first part (E2) and the second part (E2'), introducing at least one refrigerant stream (202) in the first part (E2) via at least one first inlet (21) up to a first outlet (23) arranged so that the refrigerant stream (202) flows in the first part (E2) in a descending direction opposite to the longitudinal direction (z), output of the refrigerant stream (202) introduced in step b) via the first outlet (23) of the first part (E2), introducing the refrigerant stream (201) resulting from step c) into the second part (E2') via a second inlet (51) up to a second outlet (52) of the second part (E2'), expansion of the refrigerant stream (201) resulting from step d) so as to produce a first two-phase refrigerant stream (203), introducing at least a part of the first two-phase refrigerant stream (203) into the two passages (10') of the second part (E2') via at least one third inlet (61) up to a third outlet (62), output of the first two-phase refrigerant stream (203) via the third outlet (62) in such a way as to obtain a second two-phase refrigerant stream (204), introducing at least a part of the second two-phase refrigerant stream (204) into the first part (E2) via at least one fourth inlet (41) up to a fourth outlet (42) so that the second two-phase refrigerant stream (204) flows in an ascending direction following the longitudinal direction (z) in the first passages (10), at least partially vaporising the at least one part of the first two-phase refrigerant stream (203) and the at least one part of the second two-phase refrigerant stream (204) by heat exchange with at least the hydrocarbon stream (102) so as to produce an at least partially liquefied hydrocarbon stream (220) at the outlet of the second part (E2'). According to the invention the first part (E2) has a first fluid passage cross-section (S1) defined as the product of the height (x1) and the width (y1) of a first passage (101), multiplied by the number (N1) of first passages (10) of the first part (E2), and the second part has a second fluid passage cross-section (S2) defined as the product of the height (x2) and the width (y2) of a second passage (102), multiplied by the number (N2) of second passages (10') of the second part (E2'), the heights (x1, x2) of each of the passages (10, 10') being measured in the stacking direction (x) and the widths (y1, y2) of each of the passages (10, 10') being measured in a lateral direction (y) which is orthogonal to the longitudinal direction (z) and parallel to the plates (2), the second fluid passage cross-section (S2) of the second part (E2') being less than the first fluid passage cross-section (S1) of the first part (E2).