| 摘要 |
<p>A method of rejecting nitrogen from a feed gas stream comprising methane and nitrogen so as to form a methane product comprises cooling the feed gas stream in a main heat exchanger 4 and rectifying the cooled feed gas stream in a double rectification column 12 comprising a higher pressure rectification column 14 and a lower pressure rectification column 16. A flow of gas is recycled from the lower pressure rectification column 16 to the higher pressure rectification column 14. A first part of the recycle flow is compressed in a compressor 48, is cooled, is liquefied in a condenser-reboiler and is introduced into the higher pressure rectification column 14. A second part of the recycle flow is also compressed in the compressor 48, is cooled, is liquefied in the main heat exchanger 4 or by expansion, and is introduced into the double rectification column 12 in liquid state. At least part of the cooling of both parts of the recycle gas is performed in the main heat exchanger 4. A methane product is withdrawn in liquid state from the lower pressure rectification column 16 by a pump 42. <IMAGE></p> |
