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US 2010/0132405 A1Published application
Method and system for producing LNG
AssigneeKanfa Aragon AS
InventorInge Sverre Lund Nilsen
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AssigneeKanfa Aragon AS
InventorInge Sverre Lund Nilsen
Estimating the term…
A method is described for production of LNG from an incoming feed gas (1) on an onshore or offshore installation, and it is characterised by the following steps: 1) the feed gas is led through a fractionation column (150) where it is cooled a separated in an overhead fraction with a reduced content of pentane (C5) and heavier components, and a bottom fraction enriched with heavier hydrocarbons, 2) the overhead fraction from the fractionation column is fed to a heat exchanger system (110) and is subjected to a partial condensation to form a two-phase fluid, and the two-phase fluid is separated in a suitable separator (160) a liquid (5) rich in LPG and pentane (C3-C5) which is re-circulated as cold reflux to the fractionation column (150), while the gas (6) containing lower amounts of C5 hydrocarbons and hydrocarbons heavier than C5 is exported for further processing in the heat exchanger system (110) for liquefaction to LNG with a maximum content of ethane and LPG 3) the cooling circuit for liquefaction of gas in the heat exchanger system comprises an open or closed gas expansion process with at least one gas expansion step. A system for carrying out the method is also described.
Method for production of LNG from an incoming feed gas (1), characterised by the following steps:
Method according to one of the preceding claims, characterised in that the temperature of the feed gas is reduced through the fractionation column (150) so that the temperature of the gas when it is fed into the heat exchanger system (110) is lower than the temperature of the cooling gas stream at the hot end of the heat exchanger system (hot pinch point temperature).
Method according to one of the preceding claims, characterised in that a reboiler (135) is connected to the fractionation column (150) to reduce the steam pressure of the bottom product.
Method according to one of the preceding claims, characterised in that the heat exchanger for liquefaction (LNG production) comprises one or more multi-stream heat exchangers.
Method according to one of the preceding claims, characterised in that it is carried out with a closed gas expansion process with at least one nitrogen expander.
Method according to one of the preceding claims, characterised in that it is carried out with a closed hybrid cooling process with methane/nitrogen as a cooling agent, where the cooling agent is used both in the gas phase and in the liquid phase, and where the cooling circuit has at least one gas expander and at least one appliance for expansion of a liquid cooling agent.
Method according to one of the preceding claims, characterised in that it is carried out with an open gas expansion process with at least one gas expander, in which a suitable gas at a higher pressure is used as cooling gas, and where the expanded gas at a lower pressure is not recompressed for recycling but is used for another purpose.
An optimized gas liquefaction system of the gas expansion type for the production of LNG from an incoming natural gas stream, characterised in that the system comprises:
(canceled)
(canceled)
A system according to any of claim 13-22, wherein the gas expander essentially isentropically cools the refrigerant.
A system according any of claim 13 or 16-23, wherein the liquefaction circuit comprises a closed gas expansion process with two or more gas expansion stages for essentially isentropically cooling the refrigerant by gas expansion, and where the refrigerant inlet temperature for the second gas expander stage is lower than the refrigerant inlet temperature for the first gas expander stage.
A system according to either any of claim 13 or 16-24, wherein the gaseous refrigerant comprises nitrogen gas, or a mixture of nitrogen and hydrocarbons.
Dependencies are inferred from the claim text.