Liquefaction process and apparatus
AssigneeBHP Petroleum Pty Ltd.
InventorChristopher A. T. Dubar
Life of this patent
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Abstract
Apparatus for liquefying natural gas, comprising a series of heat exchangers for cooling the natural gas in countercurrent heat exchange relationship with a refrigerant, compression means for compressing the refrigerant, expansion means for isentropically expanding at least two separate streams of the compressed refrigerant, said expanded streams of refrigerant communicating with a cool end of a respective one of the heat exchangers, and a precooling refrigeration system for precooling the natural gas to a temperature below 0° C. before it is fed to the series of heat exchangers, and for precooling the compressed refrigerant discharged from a warm end of the series of heat exchangers to a temperature below 0° C. before it is fed back into the series of heat exchangers or to the expansion means.
Claims17
Apparatus for liquefying natural gas, comprising a series of heat exchangers for cooling the natural gas in countercurrent heat exchange relationship with a refrigerant, compression means for compressing the refrigerant, expansion means for isentropically expanding at least two separate streams of the compressed refrigerant, said expanded streams of refrigerant communicating with a cool end of a respective one of the heat exchangers, and a precooling refrigeration system for precooling the natural gas to a temperature below 0° C. before it is fed to the series of heat exchangers, and for precooling the compressed refrigerant discharged from a warm end of the series of heat exchangers to a temperature below 0° C. before it is fed back into the series of heat exchangers or to the expansion means, wherein a first of said separate refrigerant streams is cooled in at least one of the series of heat exchangers, and the precooling refrigeration system is arranged to pre-cool the refrigerant prior to cooling the first refrigerant stream in the series of heat exchangers, wherein precooled refrigerant in the or each refrigerant stream other than the first is fed directly to the expansion means without any further cooling, wherein the compression means comprises multiple compressors, and further comprising a stripper column containing a heat exchanger at or near the bottom thereof, the arrangement being such that the cooled natural gas discharged from the series of heat exchangers is fed to the stripper heat exchanger to provide reboil heat for the stripper, and is subsequently fed to the stripper.
A method for liquefying natural gas comprising passing natural gas through a series of heat exchangers in countercurrent relationship with a refrigerant circulated through a work expansion cycle, said work expansion cycle comprising compressing the refrigerant, dividing and cooling the refrigerant to produce at least first and second cooled refrigerant streams, substantially isentropically expanding the first refrigerant stream to a first refrigerant temperature, substantially isentropically expanding the second refrigerant stream to a second refrigerant temperature warmer than first said refrigerant temperature, and delivering the refrigerant in the first and second refrigerant streams to a respective heat exchanger for cooling the natural gas through corresponding temperature ranges, wherein the natural gas is precooled in a precooling refrigeration system to a temperature below 0° C. before being fed to the series of heat exchangers, wherein the refrigerant discharged from a warm end of the series of heat exchangers is precooled in the precooling refrigeration system to a temperature below 0° C. after it has been compressed and before it is expanded or fed back into the series of heat exchangers, wherein a first of said refrigerant streams is cooled in at least one of the series of heat exchangers, and the precooling refrigeration system is arranged to precool the refrigerant prior to cooling the first refrigerant stream in the series of heat exchangers, wherein precooled refrigerant in the or each refrigerant stream, other than the first, is expanded in the work expansion cycle without any additional cooling, wherein the refrigerant is compressed in multi-stage compression, and wherein the refrigerant is nitrogen.
Dependencies are inferred from the claim text.