Pre-Cooling of Natural Gas by High Pressure Compression and Expansion

Abstract

A method of producing liquefied natural gas (LNG) is disclosed. A natural gas stream is provided from a supply of natural gas. The natural gas stream is compressed in at least two serially arranged compressors to a pressure of at least 2,000 psia to form a compressed natural gas stream. The compressed natural gas stream is cooled to form a cooled compressed natural gas stream. The cooled compressed natural gas stream is expanded in at least one work producing natural gas expander to a pressure that is less than 3,000 psia and no greater than the pressure to which the at least two serially arranged compressors compress the natural gas stream, to thereby form a chilled natural gas stream. The chilled natural gas stream is liquefied.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Patent Application 62 / 266,985, filed Dec. 14, 2015 entitled PRE-COOLING OF NATURAL GAS BY HIGH PRESSURE COMPRESSION AND EXPANSION, the entirety of which is incorporated by reference herein.[0002]This application is related to U.S. Provisional Patent Application No. 62 / 266,976 titled “Method and System for Separating Nitrogen from Liquefied Natural Gas Using Liquefied Nitrogen;” U.S. Provisional Patent Application No. 62 / 266,979 titled “Expander-Based LNG Production Processes Enhanced With Liquid Nitrogen;” and U.S. Provisional Patent Application No. 62 / 266,983 titled “Method of Natural Gas Liquefaction on LNG Carriers Storing Liquid Nitrogen;” all having common inventors and assignee and filed on an even date herewith, the disclosure of which is incorporated by reference herein in their entirety.FIELD OF THE INVENTION[0003]The invention relates to the liquefaction of natural gas to f...

AI Technical Summary

Benefits of technology

[0015]The invention provides a method of producing liquefied natural gas (LNG). A natural gas stream is provided from a supply of natural gas. The natural gas stream may be compressed in at least two serially arranged compressors to a pressure of at least 2,000 psia to form a compressed natural gas stream. The compressed natural gas stream may be cooled to form a cooled compressed natural gas stream. The cooled compressed natural gas stream may be expanded in at least one work producing natural gas expander to a pressure that is less than 3,000 psia and no greater than the pressure to which the at least two serially arranged compressors compress the natural gas stream, to thereby form a chilled natural gas stream. The chilled natural gas stream may then be liquefied.

[0016]The invention also provides an apparatus for the liquefaction of natural gas. At least two serially arranged compressors compress a natural gas stream to a pressure greater than 2,000 psia, thereby forming a compressed natural gas stream. A cooling element cools the compressed natural gas stream to for

Problems solved by technology

FLNG is a technology solution for monetizing offshore stranded gas where it is not economically viable to construct a gas pipeline to shore.

Although FLNG has several advantageous over conventional onshore LNG, significant technical challenges remain in the application of the technology.

For example, the required use and storage of combustible refrigerants such as propane significantly increases loss prevention issues on the FLNG.

The SMR process is also limited in capacity, which increases the number of trains needed to reach the desired LNG production.

For these reasons and others, a significant amount of topside space and weight is required for the SMR trains.

However, application of the expander-based process to an FLNG project with LNG production of greater than 2 million tons per year (MTA) has proven to be less appealing than the use of the mixed refrigerant process.

The size of the expander-based process train is limited since its refrigerant mostly remains in the vapor state throughout the entire process and the refrigerant absorbs energy through its sensible heat.

Furthermore, the limitations in compander horsepower size results in parallel rotating machinery as the capacity of the expander-based process train increases.

However, the equipment count, complexity and cost all increase with multiple expander trains.

This technol

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