Closed loop LNG process for a feed gas with nitrogen
AssigneeConocoPhillips Company
InventorsYing Zhang, Qi Ma, Wesley R. Qualls, Will T. James, Jinghua Chan
Life of this patent
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Abstract
Systems and methods for processing liquefied natural gas (LNG) can include an LNG production system with a methane refrigeration cycle downstream from an ethylene refrigeration cycle. The methane refrigeration cycle can be a closed loop methane refrigeration cycle that maintains a methane refrigerant separate from a natural gas feed, (e.g., compared to an open loop methane refrigeration cycle that extracts the methane refrigerant from the natural gas feed and recombines the methane refrigerant with the natural gas feed). The natural gas feed can be a medium or high nitrogen gas feed having a nitrogen content greater than 1.0% molarity.
Claims10
A method for cooling a natural gas feed, the method comprising:
- receiving the natural gas feed from an ethylene chiller of a liquified natural gas (LNG) process;
- condensing a methane refrigerant discharge in an ethylene heat exchanger to form a condensed methane refrigerant that is routed to one or more methane refrigerant heat exchangers;
- subcooling the natural gas feed by indirect heat exchange with the condensed methane refrigerant at the one or more methane refrigerant heat exchangers of a closed-loop refrigeration cycle to form a subcooled natural gas feed, wherein the condensed methane refrigerant is kept separate from the natural gas feed;
- reducing a pressure of the subcooled natural gas feed;
- separating a two phase stream, resulting from reducing the pressure, in an end flash vessel;
- and
- outputting an LNG product as a liquid fraction from the end flash vessel,
- wherein nitrogen is removed from the natural gas feed without utilizing a nitrogen rejection unit.
Dependencies are inferred from the claim text.