PROCESS FOR LIQUEFYING NATURAL GAS USING MIXED COOLANTS Russian patent published in 2023 - IPC F25J1/02 

FIELD: natural gas liquefaction.

SUBSTANCE: method for liquefying a purified and dried natural gas stream. Natural gas is cooled by heat exchange with mixed coolants in a cascade of three mixed coolant circuits. In the first heat exchanger of the first, second and third mixed coolant circuits, natural gas is pre-cooled, in the second heat exchanger of the second and third mixed coolant circuits, natural gas is liquefied, and in the third heat exchanger of the third mixed coolant circuit, natural gas is supercooled. When the ambient temperature changes, the composition of the mixed coolant in each circuit is regulated by directing part of the flow of the mixed coolant into the evaporation tank with a decrease in pressure to a value at which the formation of liquid and vapor phases occurs in the evaporation tank. After that, one of the phases, selected from the condition of the required change in the composition of the mixed coolant, is returned to the corresponding circuit, for which it is sent with a decrease in pressure to the evaporation space of the corresponding heat exchanger, connected to the inlet of the indicated compressor of the corresponding circuit. When the ambient air temperature changes downward, the vapor phase is selected to be returned to the circuit, and when the ambient air temperature changes upward, the liquid phase is selected to be returned to the circuit.

EFFECT: ensuring a rapid change in the composition of the mixed coolants of all circuits and the total amount of coolants in the circuits with a rapid change in ambient temperature.

8 cl, 2 dwg, 5 tbl