US 5,893,274 AGranted

Method of liquefying and treating a natural gas

AssigneeShell Research Limited

InventorsRobert Klein Nagelvoort, Kornelis Jan Vink

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Abstract

A method is provided to liquefy and treat natural gas containing components having low boiling points, the method includes: liquefying natural gas in a main heat exchanger; cooling the liquefied gas in an external heat exchanger; allowing the cooled liquefied gas to expand dynamically; introducing the expanded fluid in the upper part of a fractionation column; allowing the liquid of the expanded fluid to flow downwards thorough contacting section; withdrawing a liquid recycle stream which is passed through the heat exchanger to obtain a heated two-phase fluid; introducing the two-phase fluid in fractionation column, and allowing the vapour to flow through the contacting section; collecting the liquid of the two-phase fluid in the lower part of the fractionation column; and withdrawing therefrom a liquid product stream having a reduced content of components having low boiling points; and withdrawing from the fractionation column a gaseous stream which is enriched in components having low boiling points.

Method of liquefying and treating natural gas containing components having low boiling points, which method comprises the steps of:

(a) passing the natural gas at liquefaction pressure through the product side of a main heat exchanger;
(b) introducing cooled liquefied refrigerant at refrigerant pressure in the cold side of the main heat exchanger, allowing the cooled refrigerant to evaporate at the refrigerant pressure in the cold side of the main heat exchanger to obtain vaporous refrigerant at refrigerant pressure, and removing vaporous refrigerant from the cold side of the main heat exchanger;
(c) removing the liquefied gas at liquefaction pressure from the product side of the main heat exchanger;
(d) passing the liquefied gas through the hot side of an external heat exchanger to obtain cooled liquefied gas;
(e) allowing the cooled liquefied gas to expand to a low pressure to obtain expanded fluid, at least part of the expansion being done dynamically;
(f) introducing the expanded fluid in the upper part of a fractionation column provided with a contacting section arranged between the upper part and the lower part of the fractionation column;
(g) allowing the liquid of the expanded fluid to flow downwards through the contacting section;
(h) withdrawing from the fractionation column a liquid recycle stream which includes liquid flowing out of the contacting section;
(i) passing the liquid recycle stream through the cold side of the external heat exchanger to obtain a heated two-phase fluid;
(j) introducing at least the vapour of the two-phase fluid in the fractionation column between the lower part and the contacting section, and allowing the vapour to flow upwards through the contacting section;
(k) collecting at least part of the liquid of the two-phase fluid in a product receptacle, and withdrawing from the product receptacle a liquid product stream having a reduced content of components having low boiling points;
and
(l) withdrawing from the upper part of the fractionation column a gaseous stream which is enriched in components having low boiling points.

10 more elements

Facts

Application

08/981,015Filed 23 Dec 1997

Priority

EP 9520170923 Jun 1995

Granted

13 Apr 1999

Term ends

Not estimatedThe source records don’t support an estimate.

Classification24 codes

F25J 3/029
Separation of noble gases: of helium
F25J 1/0022
Characterised by the fluid to be liquefied: hydrocarbons, e.g. natural gas
F25J 1/0042
Using the feed stream itself or separated fractions from it, i.e. "internal refrigeration": by liquid expansion with extraction of work
F25J 1/0045
Using the feed stream itself or separated fractions from it, i.e. "internal refrigeration": by vaporising a liquid return stream

Abstract

Claims6