초록 ▼

The present invention is a process for the liquefaction of high pressure natural gas. The natural gas is expanded through a turboexpander to reduce its pressure and thereby cool it. The natural gas is then passed through a demethanizer to remove the heavier components therefrom. The natural gas is t

The present invention is a process for the liquefaction of high pressure natural gas. The natural gas is expanded through a turboexpander to reduce its pressure and thereby cool it. The natural gas is then passed through a demethanizer to remove the heavier components therefrom. The natural gas is then precooled, before substantial warming occurs, by heat exchange with a C 2 hydrocarbon refrigerant, either ethane or ethylene, contained in a single refrigerant system. The precooled natural gas is liquefied by heat exchange with a mixed refrigerant contained in a mixed refrigerant system. The mixed refrigerant consists essentially of nitrogen, methane and a C 2 hydrocarbon, either ethane or ethylene. The mixed refrigerant contained in the mixed refrigerant system is cooled by heat exchange with the C 2 hydrocarbon refrigerant contained in the single refrigerant system.

대표청구항 ▼

1. A process for liquefying natural gas comprising the steps of: (a) supplying said natural gas at a pressure above about 600 psia (4137 kPa); (b) expanding said natural gas to reduce its temperature below about -40° F. (-40° C.); (c) precooling said natural gas by heat exchange with a C 2 hydr

1. A process for liquefying natural gas comprising the steps of: (a) supplying said natural gas at a pressure above about 600 psia (4137 kPa); (b) expanding said natural gas to reduce its temperature below about -40° F. (-40° C.); (c) precooling said natural gas by heat exchange with a C 2 hydrocarbon refrigerant contained in a single refrigerant system; (d) cooling a mixed refrigerant contained in a mixed refrigerant system by heat exchange with said C 2 hydrocarbon refrigerant, wherein said mixed refrigerant consists essentially of nitrogen, methane and a C 2 hydrocarbon; and (e) liquefying said precooled natural gas by heat exchange with said mixed refrigerant. 2. The process of claim 1 wherein said natural gas is passed through a demethanizer after step (b) and before step (c). 3. The process of claim 1 wherein said natural gas is precooled in step (c) before substantial warming occurs. 4. The process of claim 1 wherein said natural gas is expanded in step (b) through a turboexpander. 5. The process of claim 1 wherein said natural gas is precooled in step (c) by at least two stages of heat exchange with said C 2 hydrocarbon refrigerant. 6. The process of claim 1 wherein said mixed refrigerant is cooled in step (d) by at least two stages of heat exchange with said C 2 hydrocarbon refrigerant. 7. The process of claim 1 wherein said precooled natural gas is liquefied in step (e) by heat exchange with said mixed refrigerant in at least two cryogenic heat exchangers. 8. The process of claim 7 wherein at least one of said cryogenic heat exchangers is a coil-wound heat exchanger. 9. The process of claim 7 wherein at least one of said cryogenic heat exchangers is a plate-fin heat exchanger. 10. A process for liquefying natural gas comprising the steps of: (a) supplying said natural gas at a pressure above about 1000 psia (6895 kPa); (b) expanding said natural gas in a turboexpander to reduce its temperature below about -60° F. (-51° C.); (c) passing said natural gas through a demethanizer to remove the heavier components therefrom; (d) precooling said natural gas, before substantial warming occurs, by at least one stage of heat exchange with a C 2 hydrocarbon refrigerant contained in a single refrigerant system; (e) cooling a mixed refrigerant contained in a mixed refrigerant system by at least three stages of heat exchange with said C 2 hydrocarbon refrigerant, wherein said mixed refrigerant consists essentially of nitrogen, methane and a C 2 hydrocarbon; and (f) liquefying said precooled natural gas by heat exchange with said mixed refrigerant in at least one cryogenic heat exchanger. 11. A process for liquefying natural gas comprising the steps of: (a) supplying said natural gas at a pressure above about 600 psia (4137 kPa); (b) expanding said natural gas in a turboexpander to reduce its temperature below about -40° F. (-40° C.); (c) passing said natural gas through a demethanizer to remove the heavier components therefrom; (d) precooling said natural gas, before substantial warming occurs, by at least three stages of heat exchange with a C 2 hydrocarbon refrigerant contained in a single refrigerant system; (e) cooling a mixed refrigerant contained in a mixed refrigerant system by at least three stages of heat exchange with said C 2 hydrocarbon refrigerant, wherein said mixed refrigerant consists essentially of nitrogen, methane and a C 2 hydrocarbon; and (f) liquefying said precooled natural gas by heat exchange with said mixed refrigerant in at least one cryogenic heat exchanger.