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US 7,059,152 B2Granted
Nitrogen rejection method and apparatus
AssigneeThe BOC Group, Inc.
InventorsJohn Douglas Oakey, Brian Morice Davies
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AssigneeThe BOC Group, Inc.
InventorsJohn Douglas Oakey, Brian Morice Davies
Estimating the term…
Nitrogen is rejected from a feed natural gas stream comprising methane and nitrogen so as to form a primary methane product. The mole fraction of nitrogen in the feed natural gas increases over a period of time. The feed natural gas stream is cooled in a main heat exchanger and is rectified in a double rectification column. A primary product methane stream and a secondary nitrogen-enriched product stream are withdrawn from the rectification column. The secondary nitrogen-enriched product stream has a mole fraction of methane at or above a chosen minimum value when the said mole fraction of nitrogen is at a minimum. When the said mole fraction of nitrogen rises to a value at which the mole fraction of methane in the secondary nitrogen-enriched product stream falls below the chosen minimum, a part of the feed gas is introduced through conduit into the secondary nitrogen-enriched product stream so as to restore its mole fraction of methane to the chosen minimum value or a value thereabove.
A method of rejecting nitrogen from a feed natural gas stream comprising methane and nitrogen so as to form a primary methane product, the moie fraction of nitrogen in the feed natural gas increasing over a period of time, the method comprising cooling said feed natural gas stream, rectifying said cooled natural feed gas stream, and withdrawing from the rectification a primary product methane stream and a secondary nitrogen-enriched product stream from the rectification, wherein said secondary nitrogen-enriched product stream has a mole fraction of methane at or above a chosen minimum value when the said mole fraction of nitrogen is at a minimum, and when the said mole fraction of nitrogen rises to a value at which the mole fraction of methane in the secondary nitrogen-enriched product stream falls below the chosen minimum, a part of the feed gas is introduced into the secondary nitrogen-enriched product stream so as to restore its mole fraction of methane to the chosen minimum value or a value thereabove.
An apparatus for rejecting nitrogen from a feed gas stream comprising methane and nitrogen, comprising a feed natural gas pipeline for obtaining the feed gas stream from a source of a mixture of nitrogen and methane whose nitrogen mole fraction can increase with the passage of time, a main heat exchanger for cooling the feed natural gas stream in communication with the feed natural gas pipeline;
Dependencies are inferred from the claim text.