Method of liquefying natural gas
First Claim
1. A method of producing a methane-rich liquid stream from a stream of natural gas predominantly consisting of methane and also containing nitrogen, comprising:
- (a) supplying said natural gas stream at a pressure above atmospheric pressure,(b) cooling and liquefying said natural gas stream using one or more refrigeration cycles,(c) expanding said liquefied natural gas to lower pressure in two or more stages in series, phase separating the gas and liquid phases produced during the expansion, thereby concentrating the nitrogen into the gas phases and producing a methane-rich and nitrogen depleted liquefied natural gas, and(d) reheating the gas phases enriched in nitrogen, and sending them out of the plant as nitrogen-enriched product streams.
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Abstract
A method of producing a methane-rich liquid stream from a stream of natural gas predominantly consisting of methane and also containing nitrogen, entailing:
(a) supplying said natural gas stream at a pressure above atmospheric pressure,
(b) cooling and liquefying said natural gas stream using one or more refrigeration cycles, and
(c) expanding said liquefied natural gas to lower pressure in two or more stages in series, phase separating the gas and liquid phases produced during the expansion, thereby concentrating the nitrogen into the vapor phase, and producing a methane-rich liquefied natural gas.
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Citations
25 Claims
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1. A method of producing a methane-rich liquid stream from a stream of natural gas predominantly consisting of methane and also containing nitrogen, comprising:
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(a) supplying said natural gas stream at a pressure above atmospheric pressure, (b) cooling and liquefying said natural gas stream using one or more refrigeration cycles, (c) expanding said liquefied natural gas to lower pressure in two or more stages in series, phase separating the gas and liquid phases produced during the expansion, thereby concentrating the nitrogen into the gas phases and producing a methane-rich and nitrogen depleted liquefied natural gas, and (d) reheating the gas phases enriched in nitrogen, and sending them out of the plant as nitrogen-enriched product streams. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of producing a methane-rich liquid stream from a stream of natural gas predominantly consisting of methane and also containing nitrogen, comprising:
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(a) supplying said natural gas stream at a pressure above atmospheric pressure, (b) providing a multicomponent refrigeration fluid composed of a mixture of components each having different boiling points, (c) compressing said multicomponent refrigeration fluid to a pressure within the range of about 250 to 1,200 psig, (d) cooling and partially condensing said multicomponent refrigeration fluid by passing it through a compressor aftercooler in heat exchange with a cooling fluid, (e) separating the liquid and vapor phases produced in the compressor aftercooler in a phase separator, (f) condensing and subcooling the vapor from the phase separator in a heat exchange apparatus, expanding the stream to low pressure and vaporizing and reheating it in heat exchange with itself and other streams in the heat exchange apparatus, (g) subcooling the liquid from the phase separator in the heat exchange apparatus, expanding it to low pressure, combining it with liquefied, expanded and reheated vapor from the phase separator, (h) vaporizing and reheating the combined stream in the heat exchange apparatus by heat exchange with itself and other streams passing through the heat exchange apparatus, (i) returning the vaporized and reheated stream for recompression according to step (c), (j) liquefying at least the major portion of the natural gas stream in the heat exchange apparatus, (k) expanding said liquefied natural gas to lower pressure in two or more stages in series, phase separating the gas and liquid phases produced during expansion, thereby concentrating the nitrogen into the gas phases and producing a methane-rich and nitrogen depleted liquefied natural gas, and (l) reheating the gas phases enriched in nitrogen, and sending them out of the plant as nitrogen-enriched product streams. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification