Patent ID: 7866184
Filing Date: 2011-01-11
Classification: F25J

Abstract:
1. A method of liquefying natural gas, said method comprising the steps of: (a) cooling the natural gas with a first refrigeration cycle employing a first refrigerant comprising less than 50 mole percent methane; (b) downstream of the first refrigeration cycle, separating the natural gas into a first lights stream and a first heavies stream in a first column; (c) separating the first heavies stream into a second lights stream and a second heavies stream in a second column; and (d) cooling the second lights stream in a methane heat exchanger via indirect heat exchange with a predominantly methane refrigerant comprising at least 50 mole percent methane, (e) cooling the first and second lights streams in a methane refrigeration cycle comprising a plurality of separate heat exchangers via indirect heat exchange with the predominantly methane refrigerant, steps (d) and (e) being performed without combining any portion of the first lights stream with the second lights stream at least until the end of the methane refrigeration cycle.