NITROGEN REJECTION METHODS AND SYSTEMS
First Claim
1. A nitrogen rejection system, comprising:
- a natural gas feed stream comprising nitrogen and methane and having a temperature above cryogenic conditions;
a feed stream heat exchanger configured to reduce the temperature of the natural gas feed stream to form a majority liquefied natural gas feed stream;
a separation unit configured to receive the cooled natural gas feed stream and produce an overhead stream enriched in nitrogen and a bottoms stream enriched in methane (“
liquefied methane stream”
); and
a liquid methane pump configured to pump the liquefied methane stream to a sales compression pressure to form a pressurized liquefied methane stream, wherein the pressurized liquefied methane stream is substantially vaporized in the feed stream heat exchanger to form a methane product stream.
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Abstract
Methods and systems for removing nitrogen from a natural gas feed stream. The systems and methods generally include a heat exchange unit, a separation unit, and a liquid methane pump unit, where the separation unit produces a liquid methane bottoms stream and a gaseous overhead stream enriched in nitrogen and the liquid methane pump unit compresses the liquid methane bottoms stream and then pumps the stream through the heat exchange unit to cool a natural gas feed stream. In some embodiments the liquid methane pump unit is a sleeve bearing type unit. Beneficially, the disclosed systems and methods incorporate high head pumps for liquid methane compression instead of vaporizing the liquid methane and compressing it in a gaseous compression units that are typically used for this purpose, saving space, materials, and power.
24 Citations
30 Claims
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1. A nitrogen rejection system, comprising:
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a natural gas feed stream comprising nitrogen and methane and having a temperature above cryogenic conditions; a feed stream heat exchanger configured to reduce the temperature of the natural gas feed stream to form a majority liquefied natural gas feed stream; a separation unit configured to receive the cooled natural gas feed stream and produce an overhead stream enriched in nitrogen and a bottoms stream enriched in methane (“
liquefied methane stream”
); anda liquid methane pump configured to pump the liquefied methane stream to a sales compression pressure to form a pressurized liquefied methane stream, wherein the pressurized liquefied methane stream is substantially vaporized in the feed stream heat exchanger to form a methane product stream. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 29)
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15. A method of nitrogen rejection, comprising:
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cooling a natural gas feed stream comprising nitrogen and methane in a feed stream heat exchanger to form a majority liquefied natural gas feed stream; separating the substantially liquefied natural gas feed stream in a separator to produce an overhead stream enriched in nitrogen and a liquid bottoms stream enriched in methane (“
liquefied methane stream”
);pressurizing the liquefied methane stream in a liquid methane pump to a sales compression pressure to form a pressurized liquefied methane stream; and exchanging heat from the natural gas feed stream to the pressurized liquefied methane stream in the feed stream heat exchanger to form a methane product stream. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30)
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Specification