NATURAL GAS LIQUEFACTION BY A HIGH PRESSURE EXPANSION PROCESS USING MULTIPLE TURBOEXPANDER COMPRESSORS

A method and system for liquefying a feed gas stream (406) including natural gas. The feed gas stream (406) is provided at a pressure less than 8.27 MPa (1,200 psia). A refrigerant stream (408) having a pressure of at least 10.3 MPa (1,500 psia) is cooled (410) and then expanded in a first expander (414) to an intermediate pressure. The first expander (414) is mechanically coupled to a first coupled compressor (438) to together form a first turboexpander-compressor. The refrigerant stream (408) is expanded in a second expander (418), which is mechanically coupled to a second coupled compressor (429) to together form a second turboexpander compressor. The refrigerant stream (408) cools the feed gas stream (406) in one or more heat exchangers (422). Using the second coupled compressor (429) and a first driven compressor (431), the refrigerant stream (408) is compressed (442) to a discharge pressure within 2.07 MPa (300 psia) of the intermediate pressure. The refrigerant stream (408) is compressed (442) using the first coupled compressor (438) and is further compressed (442) to provide the refrigerant stream (408). (Fig. 4)