Method for recovery of natural gas liquids for liquefied natural gas
First Claim
1. A process for separating a liquefied natural gas (LNG) stream containing methane and lighter components and heavy hydrocarbon components into a more volatile gas fraction containing a substantial amount of the methane and lighter components and a less volatile fraction containing a large portion of the heavy hydrocarbon components, the process comprising the steps of:
- (a) splitting the LNG stream into a first feed stream and a second feed stream;
(b) preheating at least a portion of the first feed stream to provide first tower feed stream and supplying the first tower feed stream to a fractionation tower to produce a tower overhead stream including the more volatile fraction containing the substantial amount of the methane and lighter components and a tower bottoms stream including the less volatile fraction containing the heavy hydrocarbon components;
(c) preheating at least a portion of the second feed stream to provide second tower feed stream and supplying second tower feed stream to the fractionation tower;
(d) cooling and partially condensing at least a portion of the tower overhead stream to produce a partially condensed tower overhead stream;
(e) separating the partially condensed tower overhead stream into a lean vapor stream and a tower reflux stream, and supplying the tower reflux stream to the fractionation tower;
(f) cooling the lean vapor stream such that the lean vapor stream is substantially condensed thereby producing a lean LNG stream; and
(g) pumping the lean LNG stream to a high pressure lean LNG stream.
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Abstract
The invention includes a process and apparatus for separating a liquefied natural gas (LNG) stream containing methane and lighter components and heavy hydrocarbon components into a more volatile gas fraction containing a substantial amount of the methane and lighter components and a less volatile fraction containing a large portion of the heavy hydrocarbon components. The process includes splitting the LNG stream, preheating and providing to a fractionation tower at two locations. A tower reflux stream is utilized.
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Citations
23 Claims
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1. A process for separating a liquefied natural gas (LNG) stream containing methane and lighter components and heavy hydrocarbon components into a more volatile gas fraction containing a substantial amount of the methane and lighter components and a less volatile fraction containing a large portion of the heavy hydrocarbon components, the process comprising the steps of:
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(a) splitting the LNG stream into a first feed stream and a second feed stream;
(b) preheating at least a portion of the first feed stream to provide first tower feed stream and supplying the first tower feed stream to a fractionation tower to produce a tower overhead stream including the more volatile fraction containing the substantial amount of the methane and lighter components and a tower bottoms stream including the less volatile fraction containing the heavy hydrocarbon components;
(c) preheating at least a portion of the second feed stream to provide second tower feed stream and supplying second tower feed stream to the fractionation tower;
(d) cooling and partially condensing at least a portion of the tower overhead stream to produce a partially condensed tower overhead stream;
(e) separating the partially condensed tower overhead stream into a lean vapor stream and a tower reflux stream, and supplying the tower reflux stream to the fractionation tower;
(f) cooling the lean vapor stream such that the lean vapor stream is substantially condensed thereby producing a lean LNG stream; and
(g) pumping the lean LNG stream to a high pressure lean LNG stream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A process for separating a liquefied natural gas (LNG) stream containing methane and lighter components and heavy hydrocarbon components into a more volatile gas fraction containing a substantial amount of the methane and lighter components and a less volatile fraction containing a large portion of the heavy hydrocarbon components, the process comprising the steps of:
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preheating at least a portion of the LNG stream and supplying the at least a portion of the LNG stream to a fractionation tower as a first tower feed stream to produce a tower overhead stream including the more volatile fraction containing the substantial amount of the methane and lighter components and a tower bottoms stream including the less volatile fraction containing the heavy hydrocarbon components;
expanding at least a portion of the tower overhead stream to a lower pressure such that the at least a portion of the tower overhead stream is partially condensed to produce a partially condensed low pressure vapor stream;
separating the partially condensed low pressure vapor stream into a lean vapor stream and a tower reflux stream;
compressing the lean vapor stream;
cooling the lean vapor stream to create a lean LNG stream;
cooling the tower reflux stream thereby producing a cooled lean tower reflux stream; and
pumping the lean LNG stream to a high pressure lean LNG stream. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. An apparatus for separating a liquefied natural gas (LNG) stream containing methane and lighter components and heavy hydrocarbon components into a more volatile gas fraction containing a substantial amount of the methane and lighter components and a less volatile fraction containing a large portion of the heavy hydrocarbon components, the apparatus comprising:
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means for splitting the LNG stream into a first feed stream and a second feed stream;
a first exchanger operable to preheat the first feed stream to provide a first tower feed stream;
a fractionation tower for receiving the first tower feed stream to produce a tower overhead stream including the more volatile fraction containing the substantial amount of the methane and lighter components and a tower bottoms stream including the less volatile fraction containing the heavy hydrocarbon components;
a first cooler operable to cool and partially condense at least a portion of the tower overhead stream to produce a partially condensed tower overhead stream, the first cooler operable to allow for heat exchange between the portion of the tower overhead stream and the second feed stream;
a separator operable to separate the partially condensed overhead tower stream into a lean vapor stream and a tower reflux stream, the tower reflux stream operable to return to the fractionation tower, the first exchanger being operable to allow for heat exchange between the lean vapor stream and the first feed stream, the lean vapor stream being cooled in the first exchanger to provide a lean LNG stream; and
a pump operable for pumping the lean LNG stream to a high pressure LNG stream. - View Dependent Claims (22, 23)
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Specification