Integrated Nitrogen Removal in the Production of Liquefied Natural Gas Using Intermediate Feed Gas Separation

摘要

A method and apparatus for liquefying a natural gas feed stream and removing nitrogen therefrom to produce a nitrogen-depleted LNG product, in which a natural gas feed stream is fed into the warm end of a main heat exchanger, cooled and at least partially liquefied, withdrawn from an intermediate location of the main heat exchanger and separated to form a nitrogen-enriched natural gas vapor stream and a nitrogen-depleted natural gas liquid stream, the liquid and vapor streams being reintroduced into an intermediate location of the main heat exchanger and further cooled in parallel to form a first LNG stream and a first at least partially liquefied nitrogen-enriched natural gas stream, respectively.

主权项

1. A method for producing a nitrogen-depleted LNG product, the method comprising:
(a) introducing a natural gas feed stream into the warm end of a main heat exchanger, cooling and at least partially liquefying the natural gas feed stream, and withdrawing the cooled and at least partially liquefied stream from an intermediate location of the main heat exchanger; (b) expanding, partially vaporizing and separating the cooled and at least partially liquefied stream to form a nitrogen-enriched natural gas vapor stream and a nitrogen-depleted natural gas liquid stream; (c) separately re-introducing said vapor and liquid streams into an intermediate location of the main heat exchanger, further cooling the vapor and liquid streams in parallel, the liquid stream being further cooled to form a first LNG stream and the vapor stream being further cooled and at least partially liquefied to form a first at least partially liquefied nitrogen-enriched natural gas stream, and withdrawing the first LNG stream and the first at least partially liquefied nitrogen-enriched natural gas stream from the cold end of the main heat exchanger; (d) expanding, partially vaporizing and separating the first at least partially liquefied nitrogen-enriched natural gas stream to form a nitrogen-rich vapor product and a second LNG stream; and (e) expanding, partially vaporizing and separating the second LNG stream to form a nitrogen-depleted LNG product and a nitrogen-enriched natural gas vapor.