Gas Conditioning Method and Apparatus for the Recovery of LPG/NGL(C2+) From LNG
First Claim
1. A method for recovery of liquefied petroleum gas or natural gas liquids from liquefied natural gas, the method comprising:
- splitting an input stream comprising substantially rich liquefied natural gas into a direct stream and a bypass stream;
heating said direct stream in a cross-exchanger to produce a heated rich liquefied natural gas stream;
splitting said heated rich liquefied natural gas into a primary column feed and a secondary column feed;
vaporizing at least a major portion of said secondary column feed in a vaporizer to produce a vaporized secondary column feed;
expanding said vaporized secondary column feed in an expander to produce a vaporized and expanded secondary column feed;
fractionating a top feed, said primary column feed, and said vaporized and expanded secondary column feed in a fractionation unit to produce an overhead product stream and a bottom product stream;
compressing said overhead product stream in a compressor which is coupled to said expander to produce a compressed overhead product stream;
condensing at least a major portion of said compressed overhead product stream by cooling said compressed overhead product stream in said cross-exchanger to produce a compressed and condensed overhead product stream;
directing a reflux stream of at least one of said compressed and condensed overhead product stream or an output stream to a top of said fractionation unit as said top feed;
mixing said bypass stream with a balance stream of said compressed and condensed overhead product stream to produce said output stream; and
vaporizing said output stream to produce a conditioned natural gas suitable for delivery to a pipeline or for commercial use.
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Abstract
A method and apparatus for conditioning imported liquefied natural gas to conform to a particular pipeline heating value specification and recovery of liquefied petroleum gas or natural gas liquids from liquefied natural gas are disclosed. An input stream containing liquefied natural gas is split into a direct stream and a bypass stream. The direct stream is heated in a cross-exchanger to produce a heated rich liquefied natural gas stream, which is split into a primary column feed and a secondary column feed. At least a major portion of the secondary column feed is vaporized to produce a vaporized secondary column feed, which is expanded in an expander to produce a vaporized and expanded secondary column feed. A top feed, the primary column feed, and the vaporized and expanded secondary column feed are fractionated to produce an overhead product stream and a bottom product stream. The overhead product stream is compressed in a compressor coupled to the expander. At least a major portion of the compressed overhead product stream is condensed by cooling in the cross-exchanger to produce a compressed and condensed overhead product stream. A reflux stream of at least one of the compressed and condensed overhead product stream or an output stream is directed to a top of the fractionation unit as the top feed. The bypass stream is mixed with a balance stream of the compressed and condensed overhead product stream to produce the output stream, which is vaporized to produce a conditioned natural gas product.
64 Citations
24 Claims
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1. A method for recovery of liquefied petroleum gas or natural gas liquids from liquefied natural gas, the method comprising:
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splitting an input stream comprising substantially rich liquefied natural gas into a direct stream and a bypass stream;
heating said direct stream in a cross-exchanger to produce a heated rich liquefied natural gas stream;
splitting said heated rich liquefied natural gas into a primary column feed and a secondary column feed;
vaporizing at least a major portion of said secondary column feed in a vaporizer to produce a vaporized secondary column feed;
expanding said vaporized secondary column feed in an expander to produce a vaporized and expanded secondary column feed;
fractionating a top feed, said primary column feed, and said vaporized and expanded secondary column feed in a fractionation unit to produce an overhead product stream and a bottom product stream;
compressing said overhead product stream in a compressor which is coupled to said expander to produce a compressed overhead product stream;
condensing at least a major portion of said compressed overhead product stream by cooling said compressed overhead product stream in said cross-exchanger to produce a compressed and condensed overhead product stream;
directing a reflux stream of at least one of said compressed and condensed overhead product stream or an output stream to a top of said fractionation unit as said top feed;
mixing said bypass stream with a balance stream of said compressed and condensed overhead product stream to produce said output stream; and
vaporizing said output stream to produce a conditioned natural gas suitable for delivery to a pipeline or for commercial use. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An apparatus for recovery of liquefied petroleum gas or natural gas liquids from liquefied natural gas, comprising:
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a fractionation unit for fractionating a top feed, a primary column feed, and a vaporized and expanded secondary column feed and producing an overhead product stream and a bottom product stream;
a diverter for splitting an input stream comprising substantially rich liquefied natural gas into a direct stream and a bypass stream;
a compressor for compressing said overhead product stream and producing a compressed overhead product stream;
a cross-exchanger receiving said direct stream and heating said direct stream to produce a heated rich liquefied natural gas stream while condensing at least a major portion of said compressed overhead product stream to produce a compressed and condensed overhead product stream;
a diverter for splitting said heated rich liquefied natural gas into said primary column feed and a secondary column feed;
a vaporizer for vaporizing at least a major portion of said secondary column feed and producing a vaporized secondary column feed;
an expander coupled to said compressor for expanding said vaporized secondary column feed and producing said vaporized and expanded secondary column feed;
a diverter for directing a reflux stream of at least one of said compressed and condensed overhead product stream or an output stream to a top of said fractionation unit as said top feed;
a mixer for mixing a bypass stream of said rich liquefied natural gas with a balance stream of said compressed and condensed overhead product stream to produce said output stream; and
an output vaporizer for vaporizing said output stream to produce a conditioned natural gas suitable for delivery to a pipeline or for commercial use. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification