US 12,455,114 B2
Systems and methods for removing nitrogen during liquefaction of natural gas
Will T. James, Houston, TX (US); Matthew C. Gentry, Houston, TX (US); and Wesley R. Qualls, Houston, TX (US)
Assigned to ConocoPhillips Company, Houston, TX (US)
Filed by ConocoPhillips Company, Houston, TX (US)
Filed on Nov. 9, 2020, as Appl. No. 17/092,518.
Claims priority of provisional application 62/932,119, filed on Nov. 7, 2019.
Prior Publication US 2021/0140710 A1, May 13, 2021
Int. Cl. F25J 3/06 (2006.01)
CPC F25J 3/066 (2013.01) [F25J 3/0615 (2013.01); F25J 2210/62 (2013.01); F25J 2215/60 (2013.01); F25J 2215/62 (2013.01); F25J 2215/64 (2013.01)] 19 Claims
OG exemplary drawing
 
1. A method for removing nitrogen from a natural gas stream in a liquefied natural gas facility, the method comprising:
liquefying the natural gas stream at least partially in the liquefied natural gas facility to form a liquefied natural gas stream;
routing the liquefied natural gas stream through a nitrogen rejection unit, the nitrogen rejection unit including an upstream nitrogen removal column, a downstream nitrogen removal column, an intermediate nitrogen removal column, a first condenser, and a second condenser;
condensing a nitrogen-containing stream of the liquefied natural gas stream at least partially via indirect heat exchange using the first condenser and the second condenser, each of the first condenser and the second condenser being independently a 3-stream condenser or a 2-stream condenser, the nitrogen rejection unit removing nitrogen from the liquefied natural gas stream;
routing the liquefied natural gas stream to the upstream nitrogen removal column, where a first top stream and a first bottom stream form;
routing a first portion of the first top stream to the first condenser;
removing a second portion of the first top stream from the nitrogen rejection unit;
routing a third portion of the first top stream to the intermediate nitrogen removal column;
removing the first bottom stream from the nitrogen rejection unit, the first bottom stream removed from the nitrogen rejection unit containing heavies;
routing the first portion of the first top stream from the first condenser to the intermediate nitrogen removal column, where a second top stream and a second bottom stream are formed;
routing at least a portion of the second top stream to the second condenser before routing to the downstream nitrogen removal column;
forming a third top stream and a third bottom stream in the downstream nitrogen removal column, wherein the third top stream comprises predominantly nitrogen;
routing the third bottom stream to an expansion drum;
forming a liquid stream and a gas stream using the expansion drum;
routing the liquid stream to the first condenser, the first condenser warming the liquid stream to form a warmed liquid stream before exiting the nitrogen rejection unit; and
combining the gas stream with the warmed liquid stream.